Origin of the Harappan Ernestites: Geochemical Insights into Provenance and Fabrication

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Mahala, Jyotiranjan S. Ray, A. K. Kanungo, G. N. S. Sree Bhuvan, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6780927/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 28 Nov, 2025 Read the published version in npj Heritage Science → Version 1 posted 11 You are reading this latest preprint version Abstract Advancements in stone bead technology, particularly in drilling techniques, emerged during the Indus Valley (Harappan) civilization. Long-constricted cylindrical drill bits, made from a unique stone called Ernestite, were a distinctive feature of this culture. The origin of Ernestite is a mystery due to the lack of a natural analogue and an unknown manufacturing process. This study presents a mineralogical and geochemical investigation of Ernestite stones and drill bits from several Harappan and contemporaneous sites in Gujarat, India, to uncover their origin. The isotopic ratios of Sr and Nd link the drills to the Ernestites. The texture and presence of pseudo-mullite (SiO 2 > 40 wt%) with high Al-Ti-bearing hematite suggest that Ernestites are synthetic, created through a sintering process at ~ 1100°C. An abundance of sand to silt-sized detrital quartz, along with Fe-Ti-Zr-rich minerals, indicates the use of crudely powdered sandstones and laterites as raw materials, with geochemical ties to regional sources. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction The prehistoric Indus Valley Civilization (IVC), also known as the Harappan civilization, was one of South Asia's most advanced civilizations of its time, renowned for its sophisticated urban architecture and material culture 1 – 5 . This civilization is famous for its fortified structures, efficient drainage systems, standardized seals and weights, and advanced technology employed in the manufacture of a diverse range of artifacts crafted from stone, metal, and shell 2 , 6 – 11 . Findings from nearly 2,500 sites across diverse geographic zones reveal that this civilization had broader spatial coverage compared to the contemporary Mesopotamian and Egyptian civilizations 1 , 5 , 12 , 13 . Most of the Harappan sites have been discovered along the river valleys of the Indus and Ghaggar-Hakra systems, distributed across Afghanistan, Pakistan, and northwestern India. It is generally believed that the Harappan culture began as small agro-pastoral communities in its Early phase (> 5000 − 2600 BCE), which matured into an urban civilization, recognized as the Harappan phase (2600 − 1900 BCE), demonstrating remarkable advancements in town planning, food production, and the technology of pottery and bead manufacturing. Subsequently, the society declined through de-urbanization in the Late Harappan phase (1900 − 1300 BCE) 4 , 14 – 18 . Stone beads are one of the critical indicators of cultural and trade practices within prehistoric South Asian civilizations 7 , 19 . The manufacture of stone beads began with the perforation of soft stones (e.g., limestone, steatite, and lapis lazuli) and later with hard stones (e.g., chert, agate, and jasper). The earliest evidence of stone beads dates back to the Mesolithic period (e.g., Jwalapuram) 20 ; significant developments in bead production technologies, such as drilling, shaping, coloring, and mounting onto ornaments, occurred in the Neolithic and Chalcolithic periods 2 and became a key component of regional and external trades during the Harappan civilization 7 , 9 , 14 . Ancient Gujarat was well known for its rich agate resources, which attracted the Harappans to this region, and bead manufacturing industries/workshops were established in several urban centres in Kutch and Saurashtra 14 , 21 . Although various beads of different materials were in use, the long cylindrical beads of harder stones, typically jasper and carnelian, were manufactured through perforation using constricted cylindrical drill bits cut out from unique chips/stones called Ernestites 19 , 22 – 24 , since their hardness is higher than agate (~ 7.5 on Mohs’ scale; ref. 7 , 13 , 21 ). The beads are characterized by a drill hole section with a stepped profile 7 , as the drill bits are typically wide at the tip and narrow at the mid-section (Fig. 2 b). The name “Ernestite” was given temporarily by Kenoyer and Vidale 19 after Ernst J.H. Mackay, but it remains in use. Ernestites are a signature finding of the urban phase of the Harappan civilization; however, they have been reported in large numbers from the late phase, single-cultured Harappan and Sorath Harappan sites as well 25 – 27 . Many Ernestite stones and drill bits have been found in close association with bead workshops in several Harappan sites in Pakistan (e.g., Harappa, Mahenjo-daro, Chahnudaro) 14 , 19 , 28 , 29 as well as in India (e.g., Dholavira, Khirsara, Kanmer) 24 , 26 , 27 , 30 – 32 , and in a few Sorath Harappan sites such as Bhagatrav, Bagasra, Shikarpur, Nagwada 6 , 25 , 33 . Some important Harappan and Sorath Harappan sites, including those where Ernesites have been reported, are shown on the map (Fig. 1 ). Primarily manufactured by the artisans of the Harappan civilization 7 , 34 , these unique materials almost became extinct in subsequent cultural periods 35 , 36 . Kenoyer and Vidale 19 described Ernestite at Mohenjo-daro as a rock composed of a mottled greyish-green to yellow-brown matrix with dark brown to black irregular patches or dendritic formations. Based on the XRD analysis of samples from Mohenjo-daro, Chanhudaro, and Harappa, they opined that these are metamorphic rocks composed of quartz, sillimanite, mullite, hematite, and titanium oxide phases. Law 14 observed significant quartz, mullite-sillimanite, and hematite phases in two samples from Harappa, as well as mullite and cristobalite in the other two. He found from XRD and EMPA analyses that the light and dark matrices consisted of clay-sized (< 2 µm) Al-Si bearing phases, compositionally similar to mullite and sillimanite, apart from quartz. The dark matrix contained additional phases such as hematite, titanohematite, rutile, and zircon. He suggested that the Ernestite is likely a highly indurated tonstein flint clay, sufficiently heat-treated (up to 1100°C) to yield its characteristic hardness, based on the limited mineralogical and chemical data from his study and earlier experimental studies on clays. Tonstein is a kaolinitic (flint) claystone formed by diagenesis of volcanic ash in a swampy or non-marine environment 37 . However, Law 14 did not provide the locations of the probable sources of tonstein or any experimental proof for transforming any natural rock or mineral to Ernestites by heating. His study tried to justify the presence of the constituent minerals but did not establish if all of these were produced during the heating process or if some could have been detrital. Besides, he did not explain why the so-called mullites in the Ernestites contained much less Al 2 O 3 and higher SiO 2 than stoichiometry mandated 38 . Because of the sheer number of Ernestite drill bits reported from the Harappan city of Dholavira in Gujarat (1212), Prabhakar et al. 24 hypothesized that the sources of Ernestite raw materials were located within the Kutch province of Gujarat. The XRD analyses of two samples of Ernestites from Dholavira and one sample from Bhgatrav, done by Prabhakar et al. 24 and Prasad and Prabhakar 25 , respectively, showed the presence of quartz, hematite, and sillimanite/mullite. No cristobalite has been reported in Ernestites from any of the Indian sites. An ambiguity persists about the provenance (source regions) of the Ernestite raw materials as earlier workers 14 , 24 speculated both local (Kutch/Ratanpur) and regional (Gujarat) sources, and there exists no isotopic data to establish the source(s) conclusively. Despite their ubiquitous presence in the Harappan settlements (Fig. 1 ), the origin of the Ernestite stones and drill bits remains uncertain. Hence, deciphering the Ernestite source materials and their geologic origin is vital to understanding the stone drilling technology and the inter-regional communication network during the Harappan period. In this study, we have addressed the following poorly understood aspects of the Ernestites with detailed petrography, mineralogy, mineral chemistry, geochemical and isotopic investigations from three Harappan sites (Dholavira, Khirsara, Kanmer) and one Sorath Harappan site (Bhagatrav) in Gujarat, India: (1) What is the nature of Ernestites, (2) If artificial, what raw materials were used for their manufacturing, and (3) What were the geologic sources for these raw materials? In addition, we have attempted to shed some light on the manufacturing process of these stones. Methods Owing to our limited access to the Harappan artifacts, only six samples could be included in this study, consisting of three Ernestite stone/rock samples (Fig. 2 a) and three drill bits (Fig. 2 b) from four sites (Khirsara, Kanmer, Dholavira, and Bhagatrav; Fig. 1 ) in Gujarat. The sample from Kanmer is associated with the mature Harappan phase and comes from the collection of Kharakawal et al. 31 . The Bhagatrav sample is related to the Sorath Harappan phase 39 and comes from the collection of Kanungo 40 . A sample from Dholavira represents the Mature/Late Harappan phase 30 . The stratigraphic contexts of the samples can be found in the references given for each location. The Ernestite from Bhagatrav was subsampled into three; there were two drill bits from Kanmer (the first and third from the left in Fig. 2 b) and one from Khirsara. Two laterite samples and two sandstone samples from the island of Khadir, on which Dholavira is located, were also studied. Because of their size and rarity, the drill bits were analyzed only for Sr-Nd isotopic compositions, whereas the stones/rocks were powdered for mineralogical, geochemical, and isotopic analyses. Petrographic studies were conducted on thin sections of all three Ernestite samples using transmitted and reflected light. Grain size analysis was done using the inbuilt software (Stream Basic) associated with the petrographic microscope (Olympus® BX-53). The mineralogical compositions of the Dholavira and Bhagatrav Ernestites whole rock powders were determined by X-ray diffraction (XRD) using a Bruker D2 Phaser diffractometer at the Physical Research Laboratory (PRL). The major element contents of Ernestites were determined by X-ray Fluorescence (XRF) spectroscopy using a Rigaku® Supermini200 instrument at PRL and the pressed pellet method 41 . Multiple international rock standards were used for calibration, and the reference material OU-6 from the International Association of Geoanalysts (IAG) was used for accuracy and precision checks. The major element contents of laterites and sandstones were measured at the National Centre for Earth Science Studies (NCESS), Thiruvananthapuram, using an S4 Pioneer sequential wavelength dispersive-XRF 42 , with reference materials VL-1 and MAG-1 used for accuracy and precision checks (Table S1 ). Bulk sample geochemical and isotopic measurements were carried out at PRL. About 50 mg of sample powder each was digested using conventional HF-HNO 3 and HF-HNO 3 -HCl dissolution protocols for trace element and isotopic analyses, respectively. The details of the analytical procedures are given in George and Ray 43 . Trace element concentrations were measured on a Thermo® HR-ICPMS using BHVO-2 (USGS) as a calibration standard. Machine drift correction was performed using 115 In as an internal standard. The accuracy and precision of our measurements, determined by repeated analyses of BHVO-2 (as unknown), were better than 2% for REE and 5% for other trace elements. Sr and REE were separated from digested solutions by conventional cation exchange column chromatography using AG 50W-X8 resin (BioRad®), and Nd was eluted from REE using Ln-specific resin (Eichrom®), using protocols given in George and Ray 43 . Sr and Nd isotopic ratio measurements were performed on a TIMS (Thermo® Triton Plus) in static multicollection mode. Sr isotopes of some samples were measured on an MC-ICPMS at PRL 44 . Instrumental mass fractionation for Sr and Nd isotopic ratios was corrected using exponential fractionation (internal) correction equations of Thirlwall 45 and assuming 88 Sr/ 86 Sr = 8.375209 and 146 Nd/ 144 Nd = 0.7219. Multiple measurements of SRM-987 and JNdi-1 over three years yielded an average of 87 Sr/ 86 Sr = 0.710249 ± 0.000009 (2σ; n = 14) and 143 Nd/ 144 Nd = 0.512102 ± 0.000010 (2σ; n = 14). Results Petrography and Mineralogy All Ernestite stone chips from Dholavira, Kanmer, and Bhagatrav exhibit heterogeneous physical appearances, unlike other Harappan artifacts, which demonstrate remarkable homogeneity 42 (Fig. 2 a). They are hard (harder than quartz), highly compact, do not produce streaks, and are difficult to break. Two clear domains, a yellowish-brown or khaki color phase and a black color phase, can be distinguished by the naked eye (Fig. 2 b). Transmitted and reflected light microscopy reveals that Ernestite stones contain detrital subangular to subrounded quartz grains (sand to silt-sized) and angular to sub-angular opaque phases like hematite and ilmenite set in a compact, fine-grained, light-colored (yellowish/khaki) groundmass of unidentifiable mineral(s) (Fig. 3 ). Quartz in Dholavira Ernestite occurs as fractured angular to subangular grains (Fig. 3 a,b) compared to the sub-angular to sub-rounded grains in Bhagatrav (Fig. 3 c,d) and Kanmer (Fig. 3 e,f). The opaque phases (hematite, titanohematite, and ilmenite) appear as narrow bands or irregular patches. They occur in lower proportions in the Dholavira Ernestite than in the Kanmer and Bhagatrav stones. Hematite appears gray and displays the characteristic reddish internal reflection under plane and cross-polar view, respectively, in reflected light (Fig. 3 g,h), and is often associated with ilmenite (shows bi-reflectance). All these detrital phases are essentially larger than clay-sized (~ 4 µm) mineral grains that constitute a claystone. Sand-sized (210–736 µm diameter; Supplementary Fig. 1) detrital grains of ilmenite and its partial replacement by hematite are also observed in the Kanmer Ernestite under a cross-polar view in reflected light (Fig. 3 e,f). Zircon and rutile in Kanmer Ernestite have subrounded to irregular grain boundaries, confirming their detrital nature (Supplementary Fig. 3). The size (longest diameter) distributions of detrital quartz grains (measured in the thin sections) in Dholavira, Kanmer, and Bhagatrav Ernestites are presented in a box plot (Fig. 4 ). Their ϕ (= -log 2 d; d = diameter) sizes (1.84–6.64) vary between medium sand to fine silt, with half of the distributions falling between very-fine sand to coarse silt fractions. The quartz grains in Kanmer and Dholavira stones are moderately sorted (1σ = 0.81 and 0.71, respectively), whereas those in the Bhagatrav stone are moderately well-sorted (1σ = 0.68). Powder XRD patterns of the Dholavira and Bhagatrav samples (Supplementary Fig. 2) reveal that quartz is the most abundant phase in all the samples, followed by a mullite-like phase (mullite/sillimanite). Hematite was detected only in the Bhagatrav dark matrix (Supplementary Fig. 2), though it is observed in the petrography of all Ernestites. Major and Trace elements The major oxide and trace element contents of two Ernestite samples from Bhagatrav and Dholavira, as well as two laterite and two sandstone samples from Khadir Island, are presented in Supplementary Data 1. SiO 2 content (47–61 wt%) is the highest among all oxides, with Al 2 O 3 , FeO T , and TiO 2 being other major components. MnO, Na 2 O, and P 2 O 5 are either very low (< 0.1wt%) or absent, whereas K 2 O and MgO concentrations are minor. Bhagatrav Ernestite has lower SiO 2 and Al 2 O 3 , FeO T , and TiO 2 than Dholavira Ernestite. The major oxide data of the laterite and sandstone samples from the Khadir Island are also presented in Supplementary Data 1. Laterites have high Fe 2 O 3 (36.7–37.6 wt%), moderate SiO 2 (32.31–32.61 wt%) and low Al 2 O 3 (8.77–8.89 wt%), TiO 2 (1.32–1.34 wt%) contents, whereas sandstones are characterized by high SiO 2 (67.57–68.42 wt%), moderate Al 2 O 3 (13.26–13.19), K 2 O (1.83–1.84 wt%) and low Fe 2 O 3 (2.06–2.09 wt%). Various oxides vs. SiO 2 diagrams plotted for Ernestites, sandstones, and laterites, along with the published data for Mesozoic sandstones 46 , 47 and laterites-bauxites of Kutch 48 – 50 , are presented in Fig. 5 . Figure 6 presents the primitive mantle (PM) normalized multi-element patterns for the Ernestite samples and those for Mesozoic rocks 51 , and laterites of Kutch region 50 . Table 1 Sr-Nd isotopic data for the Ernestite stones/drills and Laterites Sample Type Location 87 Sr/ 86 Sr 143 Nd/ 144 Nd ε Nd (0) E-2 Ernestite Bhagatrav 0.73022 * 0.511708 -18.1 E-3 Ernestite Bhagatrav 0.73027 * 0.511703 -18.2 E-4 Ernestite Bhagatrav 0.73087 * 0.511700 -18.3 3304 Drill bit Kanmer 0.72282 * 0.511927 -13.9 3285 Drill bit Kanmer 0.71778 * 0.511926 -13.9 ERN-KM Ernestite Kanmer 0.72207 * 0.511884 -14.7 ERN-DV Ernestite Dholavira 0.712901 0.511900 -14.4 ERN-KU Drill bit Khirsara 0.709991 0.511915 -14.1 KH-3 Laterite Khadir 0.708990 0.512256 -7.5 KH-4 Laterite Khadir 0.709551 0.512245 -7.7 KH-15-6 Sandstone Khadir 0.714940* 0.511731* -17.7 KH-15-27 Sandstone Khadir 0.743439* 0.511433* -23.5 Note: All ratios are TIMS data except those marked with *, which are MC-ICPMS data. The average isotopic ratios and external reproducibilities determined for the international SRM-987 and JNdi-1 in TIMS, after repeated analyses over three years, are 87 Sr/ 86 Sr = 0.710249 ± 0.000009 (2σ; n = 14) and 143 Nd/ 144 Nd = 0.512102 ± 0.000010 (2σ; n = 14), respectively. ε Nd (0) = [( 143 Nd/ 144 Nd) sample / 143 Nd/ 144 Nd) CHUR – 1]×10 4 , where CHUR = Chondrite Uniform Reservoir and (0) stands for present-day value. Mineral Chemistry Representative backscattered electron (BSE) images of various phases in a polished thin section of the Kanmer Ernestite are given in Supplementary Fig. 3. Mineral compositions of different phases are provided in Supplementary Data 2. X-ray elemental maps for all three Ernestite stones (i.e., Kanmer, Bhagatrav, and Dholavira), as well as chemical spot analysis data (both by EPMA), are provided in Supplementary Figs. 3–6 and Supplementary Data 2. Quartz (SiO 2 : 98–100 wt%) of varying sizes is dispersed within the light-colored (yellow) fine matrix, which is mainly composed of aluminosilicate phases (SiO 2 : 40–53 wt%; Al 2 O 3 : 40–50 wt%). Although identified as mullites by XRD, the aluminosilicate matrix phases contain much higher SiO 2 than that mandated by stoichiometry (i.e., < 30 wt%; Lentz et al., 2019), therefore, we identify these phases as pseudomullites. Fe-Ti bearing phases, such as hematite (FeO: 71–74 wt%) and ilmenite (TiO 2 : 51–56 wt%), often occur as narrow patches or are finely dispersed within the light (yellow) matrix. Many hematite grains have a high TiO2 content (29–40 wt%) and can thus be classified as titanohematite. The titanohematites also contain an appreciable amount of Al 2 O 3 (5–21 wt%). Sr-Nd isotopic ratios Results of Sr and Nd isotopic compositions of Ernestite whole rocks and drill bits, laterites, and sandstones are provided in Table 1 . The 87 Sr/ 86 Sr and ε Nd (0) of Ernestite stones and drill bits from Kutch (Dholavira, Kanmer, and Khirsara) vary between 0.71000 and 0.72282, and -14.7 and − 13.9, respectively. In contrast, the Sr-Nd isotopic compositions of Bhagatrav Ernestites are more radiogenic in Sr and less radiogenic in Nd ( 87 Sr/ 86 Sr = 0.73022 to 0.730876; ε Nd (0) = -18.3 to -18.1). The drill bits from Kanmer have an identical ε Nd (0) of -13.9, and one of the drill bits has almost identical 87 Sr/ 86 Sr as that of the Ernestite stone (0.72282 vs. 0.72207; Table 4). The laterite samples collected from the Khadir (Dholavira) have 87 Sr/ 86 Sr varying from 0.7089 to 0.7096, and their ε Nd (0) ranges from − 7.7 to -7.5, whereas the sandstones have more radiogenic Sr and Nd ( 87 Sr/ 86 Sr = 0.71494 and 0.74344; ε Nd (0) = -23.5 and − 17.7). Discussion In the first-ever detailed characterization, Kenoyer and Vidale 19 suggested a metamorphic origin for Ernestites based on their identification of the matrix phases as sillimanite and mullite. Mullite is a rare mineral and has only been reported from specific contact-metamorphic rocks (in metamorphosed clays) and pseudotachylites 52 , 53 . It is also commonly observed in high-temperature ceramics and has been synthesized by heating various aluminosilicate minerals (e.g., kaolinite, kyanite, andalusite, sillimanite) at high temperatures (> 1100°C) 54–57 . However, we identify these phases, which exhibit identical XRD spectra to mullite, as pseudomullites based on their higher SiO2 contents (> 40 wt%). Since mullite and pseudomullite are isostructural, all earlier studies, which relied primarily on XRD data, had incorrectly identified pseudomullite as mulite. "Pseudomullite" refers to a structure or phase that resembles mullite (Fig. 7 ) but is not the true, stoichiometric mullite. It can be formed by the decomposition of kaolinite or other aluminosilicate materials 57 – 59 . Mullite refers to an experimentally observed solid solution series Al 4 + 2 x Si 2−2 x O 10− x with 0.2 < x < 0.9 (Fig. 7 ) 60 , 61 . According to Shears and Archibald 38 , the stoichiometric composition of synthetic mullite commonly varies between 3Al 2 O 3 .2SiO 2 (~ 72 wt% Al 2 O 3 ) and 2Al 2 O 3 .SiO 2 (~ 78wt% Al 2 O 3 ). In natural mullites, Fe 2 O 3 substitutes Al 2 O 3 , producing a wide range of compositions at ~ 30 wt% SiO 2 (Fig. 7 ) 53 , 60 . In contrast, stoichiometric sillimanite has ~ 61 wt% Al 2 O 3 (Fig. 7 ). The aluminosilicate phase in the Ernestite matrix is pseudomullites and has higher SiO 2 and lower Al 2 O 3 than those of natural mullite or silimanite (Fig. 7 ). Pseudomullites are not found in nature and have been shown in synthetic heating experiments to be developed as an intermediate phase during kaolinite to mullite transformation at high temperature 57 , 62 (~ 1100°C). Therefore, the presence of pseudomullites unambiguously rules out that Ernestites are natural rocks, indicating their origin by high-temperature processing. The Harappans artificially produced the Ernestites as the source stones for drill bits through a high-temperature heating process that could generate the pseudomullites. Further evidence for a high-temperature process is provided by the chemical composition of Fe-Ti-bearing phases, as determined by EPMA analyses. The presence of titanohematites with significant TiO 2 (29–40 wt%) and Al 2 O 3 (5–21 wt%) suggests an extensive substitution between Fe 2 O 3 and TiO 2 and between Fe 2 O 3 and Al 2 O 3 . It is known that at temperatures below 800°C, only a limited solid solution between TiO 2 and Fe 2 O 3 is possible 63 . Similarly, in the Fe 2 O 3 -Al 2 O 3 system, higher Al 2 O 3 (up to 10 wt%) can be substituted into the hematite (Fe 2 O 3 ) structure at high temperatures only (~ 1000°C) 63 . Therefore, higher TiO 2 and Al 2 O 3 in the titanohematite confirm a heating process (> 1000°C) in Ernestite manufacturing. It is thus apparent that the pseudomullite matrix was produced during high-temperature sintering. This provides the first geochemical evidence of sintering being used in the manufacture of Ernestites. This also successfully explains the presence of high-temperature craft objects, such as stoneware bangles 64 , 65 , steatite beads 66 , and furnaces 31 , 32 , at the Harappan sites. The presence of detrital quartz grains, ilmenite, hematite, zircon, and rutile suggests that the raw materials used to make the Ernestites are natural, even though the manufacturing process was artificial. Law 14 suggested tonstein as the only raw material for Harappan Ernestites. He attributed the coarser (up to 100 µm) subhedral quartz or cristobalite grains (detected in his BSE images) to the recrystallized free silica (released during heating) and zircon to a magmatic origin. He further proposed that the raw materials for the Ernsitites (i.e, tonsteins) were sourced from local/regional sources (i.e., Kutch). Tonsteins are hard and compact kaolinite-altered volcanic ash layers, generally found in coals and associated sediments 37 . These often contain magmatic quartz and zircon 37 , 67 . However, microtextural characteristics of these constituent minerals suggest that zircon, quartz, ilmenite, and rutile in Ernestites are essentially detrital. Therefore, tonstein is ruled out as Ernestite's raw material. Additional evidence against using tonsteins for Ernestites comes from the presence of non-radiogenic Nd in the Ernestites (ε Nd (0) -11, Fig. 8 ). Besides, our Ernestite samples contain sand-sized detrital quartz and ilmenite grains in contrast to a claystone/tonstein that usually contains clay-sized grains (≤ 2µm). The detrital quartz grains' size and moderately sorted nature suggest using coarser raw materials, such as sandstones, which were likely pounded into sand/silt-sized particles before being processed for sintering. It is possible that the Fe-Ti phases (hematite, titanohematite, ilmenite, and rutile) observed in the Ernestites also originated from the sandstones, as sandstones generally contain such heavy minerals. However, our Ernestites appear to exhibit mixing trends between Mesozoic sandstones and laterites-bauxites of the Kutch region in various oxide vs. SiO 2 plots (Fig. 5 ). Trace element patterns (Fig. 6 ) also suggest that such a mixture is necessary to explain the chemistry of the Ernestites. Besides, high contents of Al 2 O 3 (> 20 wt%) and high field strength elements (e.g., Sc, V, Cr, and Co) in Ernestites cannot be achieved by the sandstones of the Kutch alone. Therefore, a second end-member, containing Fe-Ti minerals but low in alkali elements, is needed to explain the Ernestite chemistry, and the laterites of Kutch, derived from the mafic volcanic rocks of the Deccan Traps, fit the bill. The Paleocene to Eocene lateritic deposits in western Kutch (Matanomadh Formation) and Saurashtra (Jamnagar) contain both Al-rich (gibbsite, kaolinite) and Fe-rich (goethite, hematite, ilmenite-rich) phases and are depleted in alkalis 48 – 50 , and have the required characteristics of this raw material. Although we discard claystone as the sole raw material, we do not deny its possible use in combination with sandstone and laterite for Ernestite manufacturing. Since kaolinite is a common mineral in laterites, it could have decomposed and undergone subsequent chemical and structural changes to form the pseudomullite matrix during the sintering process. The free (amorphous) silica released during the heating of pure kaolinite recrystallizes as cristobalite upon further heating (to ~ 1350°C) 57 and when kaolinite is heated with alumina-bearing material (e.g., bauxite, aluminum fluoride, aluminum hydroxide), free silica formation is prohibited 68 – 70 . We suspect that during the sintering process carried out by the Harappans, the free silica (SiO 2 ) formation was suppressed by the presence of gibbsite (Al(OH) 3 ) in the laterite. Moreover, gibbsite undergoes thermal decomposition to boehmite (AlO.OH) at 200°C, which transforms into a transitional alumina (α- Al 2 O 3 ) phase at 500°C 71 , 72 . We suspect that the Al 2 O 3 in the titanohematite structure was sourced from gibbsite (lateritic) in the mixture during the α-Al 2 O 3 stage. Since the results of our study point to a maximum temperature of 1100°C for the sintering process, the cristobalites observed by Law 14 likely represent a higher temperature or longer heating process. Similar 87 Sr/ 86 Sr and ε Nd (0) of Ernestite stone and drill bits from Kanmer genetically link the drill bits to the stone. Although it has been well established that Ernestite stones are the raw materials for long and constricted cylindrical drill bits 14 , their isotopic similarity is the first-ever chemical evidence for the same. Because of the sheer number of Ernestite stones and drill bits from Dholavira, Law 14 speculated that the raw materials for the stones came from either the island itself (i.e., Khadir) or the Kutch region of Gujarat. However, our geochemical data (Figs. 5 and 6 ) support a regional sourcing of the raw materials. The sandstones and laterites of Kutch appear to have been the primary sources of the raw materials for the Ernestites. In search of more robust evidence for this geological provenance hypothesis, we make use of the Sr-Nd isotopic compositions of Ernestites and their potential source rocks (Table 1 ; Fig. 8 ). Although, the ε Nd and 87 Sr/ 86 Sr compositions of the Ernestites plot well within the compositional field of the Mesozoic sandstones of Kutch, they can be explained by a two-component mixing between the sandstones and laterites of Khadir (Fig. 8 ). The isotopic compositions of laterites of Khadir, which are developed over volcanic ash of Deccan Traps fall well within the field of the Deccan Basalts, which suggests that other lateritic horizons in the Kutch and Saurashtra region, developed over Deccan Trap rocks could also have served as sources for the raw material for Ernestites. The mixing model suggests 55–60% contribution from these end-members to the isotopic compositions of most of our samples; however, those from Bhagatrav (in south Gujarat) require ~ 80% contribution from the sandstones. Therefore, we infer that the Harappans used laterite from different weathered (Deccan) horizons and sand from Mesozoic sandstones from Kutch to manufacture Ernestites. We make the following conclusions based on our investigation of Ernestites, the parent material for the unique constricted drill bits of the Harappan Civilization, using petrographic, mineralogical, geochemical, and Sr-Nd isotopic techniques. Stone drill bits have been isotopically fingerprinted to the Ernestites, confirming their genetic link. The Ernestites consist of medium sand to fine silt detrital quartz, hematite, ilmenite, zircon, and rutile welded together in a fine-grained aluminosilicate matrix/groundmass. Ernestites’ texture (larger mineral grains and their detrital nature), and its whole-rock Nd isotopic composition (ε Nd (0) > -11) rule out the use of tonstein flint as a raw material. The aluminosilicate matrix/groundmass phase has been chemically identified as pseudomullite, though its XRD spectrum is similar to mullite. The presence of pseudomullites, with high SiO 2 contents (> 40 wt%), unambiguously makes Ernestites artificial, with supporting evidence from the significant substitution of Al 2 O 3 and TiO 2 in hematites. These data also suggest a high temperature (reaching 1100°C) synthesis of Ernestites. Mineralogy, texture, and mineral chemistry suggest Ernestites were manufactured through a high-temperature sintering process involving sand and clay-bearing raw materials. Major and trace elements and Sr-Nd isotopic data point to the likelihood of the raw materials' regional provenance (sandstones and laterites of Kutch). All our findings suggest that Ernestites were likely made in the Harappan centres of Gujarat, India, and the Ernestite-based drilling technology was exclusive to this civilization. Declarations Competing interests The authors declare no competing interests related to this work. Author Contribution J.S.R and A.C. conceived the study. A.K.K., Y.S.R., J.S.K., and S.V.R .supplied samples. A.C., M.K.M., B.G.G., N.S., and G.N.S.S.B. conducted the analytical work. M.K.M., G.N.S.S.B., A.C., and J.S.R. interpreted the data. J.S.R. secured the project’s funding, and all authors contributed to the writing. Acknowledgement JSR thanks the Physical Research Laboratory, Ahmedabad, India, for funding. The authors acknowledge the laboratory support of Sneha Mukherjee of NCESS and Jitender Kumar of PRL. Data Availability Statement All data generated for this study are in the tables in the manuscript and the supplementary files. References Ramesh S. The Indus Valley Civilisation: 3000 BC to 1600 BC. 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Supplementary Files SupplementaryData1.xlsx Supplementary Data 1 (Excel file containing Major and Trace element data for Ernestites) SupplementaryData2.xlsx Supplementary Data 2 (Mineral chemistry - EMPA data for various phases in Ernestites) SupplementaryFigures.docx Supplementary Figures (Supplementary Figures 1-6) Cite Share Download PDF Status: Published Journal Publication published 28 Nov, 2025 Read the published version in npj Heritage Science → Version 1 posted Editorial decision: Revision requested 14 Jul, 2025 Reviews received at journal 11 Jul, 2025 Reviews received at journal 05 Jul, 2025 Reviews received at journal 03 Jul, 2025 Reviewers agreed at journal 22 Jun, 2025 Reviewers agreed at journal 21 Jun, 2025 Reviewers agreed at journal 19 Jun, 2025 Reviewers invited by journal 18 Jun, 2025 Editor assigned by journal 11 Jun, 2025 Submission checks completed at journal 10 Jun, 2025 First submitted to journal 10 Jun, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6780927","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":473681892,"identity":"01c5feb3-dc8c-478f-8c7e-7db5fb702162","order_by":0,"name":"Milan K. 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Rajesh","email":"","orcid":"","institution":"University of Kerala","correspondingAuthor":false,"prefix":"","firstName":"S.","middleName":"V.","lastName":"Rajesh","suffix":""}],"badges":[],"createdAt":"2025-05-30 04:39:04","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6780927/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6780927/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s40494-025-02147-2","type":"published","date":"2025-11-28T15:56:56+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":85075356,"identity":"7cce0aa9-4d7d-4bd8-8617-51683a02b06e","added_by":"auto","created_at":"2025-06-20 16:29:52","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":166168,"visible":true,"origin":"","legend":"\u003cp\u003eA schematic geographical map of western India and Pakistan shows important Harappan urban centers and cities yielding Ernestite stones and drill bits. The four Harappan sites whose Ernestite samples have been studied in this work are marked.\u003c/p\u003e","description":"","filename":"OnlineFig1.png","url":"https://assets-eu.researchsquare.com/files/rs-6780927/v1/78bcefc1216b1a797487b674.png"},{"id":85075363,"identity":"6d9993f8-7c29-4234-88d0-c448f8db05e5","added_by":"auto","created_at":"2025-06-20 16:29:52","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":7386212,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Ernestite stones from Dholavira, Bhagatrav, and Kanmer studied in this work. Note the compositional variations between different samples, as reflected in their colors. (b) Ernestite drill bits from Kanmer. Note the compositional variations. The first and third samples have been used for isotopic analyses.\u003c/p\u003e","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6780927/v1/27a172a98ae98cb853dc129b.jpg"},{"id":85075766,"identity":"aba6daa8-a232-4562-b323-10094b7a187e","added_by":"auto","created_at":"2025-06-20 16:37:52","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":25174029,"visible":true,"origin":"","legend":"\u003cp\u003ePhotomicrographs of Ernestite thin sections: (a) sample from Dholavira in plane-polarized transmitted light showing the presence of quartz (Qz) and opaques (Opq); (b) same as in (a) with hematite (Hem) displaying characteristic red internal reflection under reflected lights; (c-d) sample from Bhagatrav in plane-polarized and cross-polarized transmitted lights; (e-f) sample from Kanmer showing detrital ilmenite (Ilm) and quartz (Qz) in plane-polarized transmitted light; (g-h) sand-sized ilmenite (Ilm) grains and hematite (Hem) patches in the same sample as in (e) in plane and crossed polarized reflected lights, respectively.\u003c/p\u003e","description":"","filename":"Fig3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6780927/v1/06e9b6d7da4fe51a35aeeacc.jpg"},{"id":85076531,"identity":"32b91317-973f-4146-9878-08c87937e419","added_by":"auto","created_at":"2025-06-20 16:45:52","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":270393,"visible":true,"origin":"","legend":"\u003cp\u003eBoxplot showing grain size distribution (in ϕ scale) in the Ernestites. Relevant statistical information is given in boxes inside the figure. The mean (square) and median (red dashed line) are marked in each box. Bhagatrav-1 and Bhagatrav-2 represent the yellow (khaki) and black colored groundmasses, respectively. Symbols: n= number of observations; µ = mean; σ = standard deviation; SK = skewness; K = Kurtosis.\u003c/p\u003e","description":"","filename":"Fig4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6780927/v1/991e582b15e30ed332779eb9.jpg"},{"id":85075361,"identity":"d217c47e-fd5a-4123-8bb2-f74261381ae0","added_by":"auto","created_at":"2025-06-20 16:29:52","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":247300,"visible":true,"origin":"","legend":"\u003cp\u003ePlots of various oxides vs SiO\u003csub\u003e2\u003c/sub\u003e for Ernestites of Gujarat, laterites, and sandstones from Khadir Island (data in Table 1). Compositions of Mesozoic sandstones, laterites, and bauxites of Kutch are plotted as fields for comparison. Data from ref. \u003csup\u003e46–50\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"Fig5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6780927/v1/94dbe3b832e0e457481f2518.jpg"},{"id":85075761,"identity":"8c332235-460a-4731-a187-8d2462a5b861","added_by":"auto","created_at":"2025-06-20 16:37:52","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1449304,"visible":true,"origin":"","legend":"\u003cp\u003ePrimitive Mantle normalized spider diagram for Ernestites of Gujarat. Also plotted are the data for Mesozoic shales and laterites of Kutch (Data from ref. \u003csup\u003e48,51\u003c/sup\u003e. Normalizing values are from \u003csup\u003e73,74\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"Fig6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6780927/v1/35029c042de1581892809898.jpg"},{"id":85075767,"identity":"7bf3d7dd-87b9-4c3c-adc0-38f0994ace5d","added_by":"auto","created_at":"2025-06-20 16:37:52","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":253457,"visible":true,"origin":"","legend":"\u003cp\u003eThe plot of Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e vs. SiO\u003csub\u003e2\u003c/sub\u003e for the aluminosilicate phases in our Ernestite samples compared with compositions of natural mullite, stoichiometric (synthetic) mullite, mullite solid solution, and stoichiometric sillimanite. Data for Natural mullite from ref. \u003csup\u003e53,60\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"Fig7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6780927/v1/7782e4de10de9a52e6d1ae29.jpg"},{"id":85075378,"identity":"8f1a7ad8-20e8-46e6-a689-be1582d4ebe0","added_by":"auto","created_at":"2025-06-20 16:29:52","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":254712,"visible":true,"origin":"","legend":"\u003cp\u003eThe plot of ε\u003csub\u003eNd\u003c/sub\u003e(0) vs. \u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr of the Ernestite stones and drill bits, along with laterites and sandstones from Khadir Island. The compositional fields for Deccan Basalts and Mesozoic sedimentary rocks (sandstones) of Kutch are also shown for comparison. The curves represent binary mixing curves between a sandstone (\u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr = 0.743415; ε\u003csub\u003eNd\u003c/sub\u003e = -23.5) and a laterite (\u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr = 0.70927; ε\u003csub\u003eNd\u003c/sub\u003e = -7.6). The sandstone end-member (A) composition is similar to a Mesozoic sandstone of Kutch, and the laterite (B) is from Khadir (Table 4); \u003cem\u003ef\u003c/em\u003e represents the fraction of sand end-member in the mixture. Data for Deccan Basalts: ref. \u003csup\u003e75–81\u003c/sup\u003e and Mesozoic sandstones: ref. \u003csup\u003e82\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"Fig8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6780927/v1/ebcc1657fcf8ce450221a916.jpg"},{"id":97178429,"identity":"371a3564-5402-40a8-ab4b-cf262e58c2c1","added_by":"auto","created_at":"2025-12-01 16:09:54","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":32692871,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6780927/v1/69264b52-31d0-4027-afa3-346968d51fd6.pdf"},{"id":85075357,"identity":"9bf59083-a16e-4462-b4c5-774a2570c5d9","added_by":"auto","created_at":"2025-06-20 16:29:52","extension":"xlsx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":22230,"visible":true,"origin":"","legend":"\u003cp\u003eSupplementary Data 1 (Excel file containing Major and Trace element data for Ernestites)\u003c/p\u003e","description":"","filename":"SupplementaryData1.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-6780927/v1/a2b3734ee80b6224bbbb9978.xlsx"},{"id":85075358,"identity":"a90ae64e-3272-4e26-b4c3-b3eee13c82d0","added_by":"auto","created_at":"2025-06-20 16:29:52","extension":"xlsx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":38053,"visible":true,"origin":"","legend":"\u003cp\u003eSupplementary Data 2 (Mineral chemistry - EMPA data for various phases in Ernestites)\u003c/p\u003e","description":"","filename":"SupplementaryData2.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-6780927/v1/ee972d097edf9d2e80158824.xlsx"},{"id":85075768,"identity":"8abb87be-85b0-45ee-86e1-3d883a82e891","added_by":"auto","created_at":"2025-06-20 16:37:52","extension":"docx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":15480811,"visible":true,"origin":"","legend":"\u003cp\u003eSupplementary Figures (Supplementary Figures 1-6)\u003c/p\u003e","description":"","filename":"SupplementaryFigures.docx","url":"https://assets-eu.researchsquare.com/files/rs-6780927/v1/851cd710bed0ddf1c570bc01.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Origin of the Harappan Ernestites: Geochemical Insights into Provenance and Fabrication","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe prehistoric Indus Valley Civilization (IVC), also known as the Harappan civilization, was one of South Asia's most advanced civilizations of its time, renowned for its sophisticated urban architecture and material culture\u003csup\u003e\u003cspan additionalcitationids=\"CR2 CR3 CR4\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. This civilization is famous for its fortified structures, efficient drainage systems, standardized seals and weights, and advanced technology employed in the manufacture of a diverse range of artifacts crafted from stone, metal, and shell\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan additionalcitationids=\"CR7 CR8 CR9 CR10\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. Findings from nearly 2,500 sites across diverse geographic zones reveal that this civilization had broader spatial coverage compared to the contemporary Mesopotamian and Egyptian civilizations\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. Most of the Harappan sites have been discovered along the river valleys of the Indus and Ghaggar-Hakra systems, distributed across Afghanistan, Pakistan, and northwestern India. It is generally believed that the Harappan culture began as small agro-pastoral communities in its Early phase (\u0026gt;\u0026thinsp;5000\u0026thinsp;\u0026minus;\u0026thinsp;2600 BCE), which matured into an urban civilization, recognized as the Harappan phase (2600\u0026thinsp;\u0026minus;\u0026thinsp;1900 BCE), demonstrating remarkable advancements in town planning, food production, and the technology of pottery and bead manufacturing. Subsequently, the society declined through de-urbanization in the Late Harappan phase (1900\u0026thinsp;\u0026minus;\u0026thinsp;1300 BCE)\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan additionalcitationids=\"CR15 CR16 CR17\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eStone beads are one of the critical indicators of cultural and trade practices within prehistoric South Asian civilizations\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. The manufacture of stone beads began with the perforation of soft stones (e.g., limestone, steatite, and lapis lazuli) and later with hard stones (e.g., chert, agate, and jasper). The earliest evidence of stone beads dates back to the Mesolithic period (e.g., Jwalapuram)\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e; significant developments in bead production technologies, such as drilling, shaping, coloring, and mounting onto ornaments, occurred in the Neolithic and Chalcolithic periods\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e and became a key component of regional and external trades during the Harappan civilization\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. Ancient Gujarat was well known for its rich agate resources, which attracted the Harappans to this region, and bead manufacturing industries/workshops were established in several urban centres in Kutch and Saurashtra\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. Although various beads of different materials were in use, the long cylindrical beads of harder stones, typically jasper and carnelian, were manufactured through perforation using constricted cylindrical drill bits cut out from unique chips/stones called Ernestites\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan additionalcitationids=\"CR23\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e, since their hardness is higher than agate (~\u0026thinsp;7.5 on Mohs\u0026rsquo; scale; ref. \u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e). The beads are characterized by a drill hole section with a stepped profile\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e, as the drill bits are typically wide at the tip and narrow at the mid-section (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe name \u0026ldquo;Ernestite\u0026rdquo; was given temporarily by Kenoyer and Vidale\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e after Ernst J.H. Mackay, but it remains in use. Ernestites are a signature finding of the urban phase of the Harappan civilization; however, they have been reported in large numbers from the late phase, single-cultured Harappan and Sorath Harappan sites as well\u003csup\u003e\u003cspan additionalcitationids=\"CR26\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. Many Ernestite stones and drill bits have been found in close association with bead workshops in several Harappan sites in Pakistan (e.g., Harappa, Mahenjo-daro, Chahnudaro)\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e as well as in India (e.g., Dholavira, Khirsara, Kanmer)\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e,\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e,\u003cspan additionalcitationids=\"CR31\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e, and in a few Sorath Harappan sites such as Bhagatrav, Bagasra, Shikarpur, Nagwada\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. Some important Harappan and Sorath Harappan sites, including those where Ernesites have been reported, are shown on the map (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Primarily manufactured by the artisans of the Harappan civilization\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e, these unique materials almost became extinct in subsequent cultural periods\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e,\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eKenoyer and Vidale\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e described Ernestite at Mohenjo-daro as a rock composed of a mottled greyish-green to yellow-brown matrix with dark brown to black irregular patches or dendritic formations. Based on the XRD analysis of samples from Mohenjo-daro, Chanhudaro, and Harappa, they opined that these are metamorphic rocks composed of quartz, sillimanite, mullite, hematite, and titanium oxide phases. Law\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e observed significant quartz, mullite-sillimanite, and hematite phases in two samples from Harappa, as well as mullite and cristobalite in the other two. He found from XRD and EMPA analyses that the light and dark matrices consisted of clay-sized (\u0026lt;\u0026thinsp;2 \u0026micro;m) Al-Si bearing phases, compositionally similar to mullite and sillimanite, apart from quartz. The dark matrix contained additional phases such as hematite, titanohematite, rutile, and zircon. He suggested that the Ernestite is likely a highly indurated tonstein flint clay, sufficiently heat-treated (up to 1100\u0026deg;C) to yield its characteristic hardness, based on the limited mineralogical and chemical data from his study and earlier experimental studies on clays. Tonstein is a kaolinitic (flint) claystone formed by diagenesis of volcanic ash in a swampy or non-marine environment\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. However, Law\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e did not provide the locations of the probable sources of tonstein or any experimental proof for transforming any natural rock or mineral to Ernestites by heating. His study tried to justify the presence of the constituent minerals but did not establish if all of these were produced during the heating process or if some could have been detrital. Besides, he did not explain why the so-called mullites in the Ernestites contained much less Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and higher SiO\u003csub\u003e2\u003c/sub\u003e than stoichiometry mandated\u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eBecause of the sheer number of Ernestite drill bits reported from the Harappan city of Dholavira in Gujarat (1212), Prabhakar et al.\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e hypothesized that the sources of Ernestite raw materials were located within the Kutch province of Gujarat. The XRD analyses of two samples of Ernestites from Dholavira and one sample from Bhgatrav, done by Prabhakar et al.\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e and Prasad and Prabhakar\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e, respectively, showed the presence of quartz, hematite, and sillimanite/mullite. No cristobalite has been reported in Ernestites from any of the Indian sites. An ambiguity persists about the provenance (source regions) of the Ernestite raw materials as earlier workers\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e speculated both local (Kutch/Ratanpur) and regional (Gujarat) sources, and there exists no isotopic data to establish the source(s) conclusively.\u003c/p\u003e \u003cp\u003eDespite their ubiquitous presence in the Harappan settlements (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003e), the origin of the Ernestite stones and drill bits remains uncertain. Hence, deciphering the Ernestite source materials and their geologic origin is vital to understanding the stone drilling technology and the inter-regional communication network during the Harappan period. In this study, we have addressed the following poorly understood aspects of the Ernestites with detailed petrography, mineralogy, mineral chemistry, geochemical and isotopic investigations from three Harappan sites (Dholavira, Khirsara, Kanmer) and one Sorath Harappan site (Bhagatrav) in Gujarat, India: (1) What is the nature of Ernestites, (2) If artificial, what raw materials were used for their manufacturing, and (3) What were the geologic sources for these raw materials? In addition, we have attempted to shed some light on the manufacturing process of these stones.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eOwing to our limited access to the Harappan artifacts, only six samples could be included in this study, consisting of three Ernestite stone/rock samples (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003ea) and three drill bits (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003eb) from four sites (Khirsara, Kanmer, Dholavira, and Bhagatrav; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003e) in Gujarat. The sample from Kanmer is associated with the mature Harappan phase and comes from the collection of Kharakawal et al.\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. The Bhagatrav sample is related to the Sorath Harappan phase\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e and comes from the collection of Kanungo\u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e. A sample from Dholavira represents the Mature/Late Harappan phase\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. The stratigraphic contexts of the samples can be found in the references given for each location. The Ernestite from Bhagatrav was subsampled into three; there were two drill bits from Kanmer (the first and third from the left in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003eb) and one from Khirsara. Two laterite samples and two sandstone samples from the island of Khadir, on which Dholavira is located, were also studied. Because of their size and rarity, the drill bits were analyzed only for Sr-Nd isotopic compositions, whereas the stones/rocks were powdered for mineralogical, geochemical, and isotopic analyses.\u003c/p\u003e \u003cp\u003ePetrographic studies were conducted on thin sections of all three Ernestite samples using transmitted and reflected light. Grain size analysis was done using the inbuilt software (Stream Basic) associated with the petrographic microscope (Olympus\u0026reg; BX-53). The mineralogical compositions of the Dholavira and Bhagatrav Ernestites whole rock powders were determined by X-ray diffraction (XRD) using a Bruker D2 Phaser diffractometer at the Physical Research Laboratory (PRL).\u003c/p\u003e \u003cp\u003eThe major element contents of Ernestites were determined by X-ray Fluorescence (XRF) spectroscopy using a Rigaku\u0026reg; Supermini200 instrument at PRL and the pressed pellet method\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. Multiple international rock standards were used for calibration, and the reference material OU-6 from the International Association of Geoanalysts (IAG) was used for accuracy and precision checks. The major element contents of laterites and sandstones were measured at the National Centre for Earth Science Studies (NCESS), Thiruvananthapuram, using an S4 Pioneer sequential wavelength dispersive-XRF\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e, with reference materials VL-1 and MAG-1 used for accuracy and precision checks (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eBulk sample geochemical and isotopic measurements were carried out at PRL. About 50 mg of sample powder each was digested using conventional HF-HNO\u003csub\u003e3\u003c/sub\u003e and HF-HNO\u003csub\u003e3\u003c/sub\u003e-HCl dissolution protocols for trace element and isotopic analyses, respectively. The details of the analytical procedures are given in George and Ray\u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. Trace element concentrations were measured on a Thermo\u0026reg; HR-ICPMS using BHVO-2 (USGS) as a calibration standard. Machine drift correction was performed using \u003csup\u003e115\u003c/sup\u003eIn as an internal standard. The accuracy and precision of our measurements, determined by repeated analyses of BHVO-2 (as unknown), were better than 2% for REE and 5% for other trace elements. Sr and REE were separated from digested solutions by conventional cation exchange column chromatography using AG 50W-X8 resin (BioRad\u0026reg;), and Nd was eluted from REE using Ln-specific resin (Eichrom\u0026reg;), using protocols given in George and Ray\u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. Sr and Nd isotopic ratio measurements were performed on a TIMS (Thermo\u0026reg; Triton Plus) in static multicollection mode. Sr isotopes of some samples were measured on an MC-ICPMS at PRL\u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e. Instrumental mass fractionation for Sr and Nd isotopic ratios was corrected using exponential fractionation (internal) correction equations of Thirlwall\u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e and assuming \u003csup\u003e88\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr = 8.375209 and \u003csup\u003e146\u003c/sup\u003eNd/\u003csup\u003e144\u003c/sup\u003eNd = 0.7219. Multiple measurements of SRM-987 and JNdi-1 over three years yielded an average of \u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr = 0.710249\u0026thinsp;\u0026plusmn;\u0026thinsp;0.000009 (2σ; n\u0026thinsp;=\u0026thinsp;14) and \u003csup\u003e143\u003c/sup\u003eNd/\u003csup\u003e144\u003c/sup\u003eNd = 0.512102\u0026thinsp;\u0026plusmn;\u0026thinsp;0.000010 (2σ; n\u0026thinsp;=\u0026thinsp;14).\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003ePetrography and Mineralogy\u003c/h2\u003e \u003cp\u003eAll Ernestite stone chips from Dholavira, Kanmer, and Bhagatrav exhibit heterogeneous physical appearances, unlike other Harappan artifacts, which demonstrate remarkable homogeneity\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). They are hard (harder than quartz), highly compact, do not produce streaks, and are difficult to break. Two clear domains, a yellowish-brown or khaki color phase and a black color phase, can be distinguished by the naked eye (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). Transmitted and reflected light microscopy reveals that Ernestite stones contain detrital subangular to subrounded quartz grains (sand to silt-sized) and angular to sub-angular opaque phases like hematite and ilmenite set in a compact, fine-grained, light-colored (yellowish/khaki) groundmass of unidentifiable mineral(s) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Quartz in Dholavira Ernestite occurs as fractured angular to subangular grains (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea,b) compared to the sub-angular to sub-rounded grains in Bhagatrav (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec,d) and Kanmer (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee,f). The opaque phases (hematite, titanohematite, and ilmenite) appear as narrow bands or irregular patches. They occur in lower proportions in the Dholavira Ernestite than in the Kanmer and Bhagatrav stones. Hematite appears gray and displays the characteristic reddish internal reflection under plane and cross-polar view, respectively, in reflected light (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eg,h), and is often associated with ilmenite (shows bi-reflectance). All these detrital phases are essentially larger than clay-sized (~\u0026thinsp;4 \u0026micro;m) mineral grains that constitute a claystone. Sand-sized (210\u0026ndash;736 \u0026micro;m diameter; Supplementary Fig.\u0026nbsp;1) detrital grains of ilmenite and its partial replacement by hematite are also observed in the Kanmer Ernestite under a cross-polar view in reflected light (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee,f). Zircon and rutile in Kanmer Ernestite have subrounded to irregular grain boundaries, confirming their detrital nature (Supplementary Fig.\u0026nbsp;3). The size (longest diameter) distributions of detrital quartz grains (measured in the thin sections) in Dholavira, Kanmer, and Bhagatrav Ernestites are presented in a box plot (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Their ϕ (= -log\u003csub\u003e2\u003c/sub\u003ed; d\u0026thinsp;=\u0026thinsp;diameter) sizes (1.84\u0026ndash;6.64) vary between medium sand to fine silt, with half of the distributions falling between very-fine sand to coarse silt fractions. The quartz grains in Kanmer and Dholavira stones are moderately sorted (1σ\u0026thinsp;=\u0026thinsp;0.81 and 0.71, respectively), whereas those in the Bhagatrav stone are moderately well-sorted (1σ\u0026thinsp;=\u0026thinsp;0.68). Powder XRD patterns of the Dholavira and Bhagatrav samples (Supplementary Fig.\u0026nbsp;2) reveal that quartz is the most abundant phase in all the samples, followed by a mullite-like phase (mullite/sillimanite). Hematite was detected only in the Bhagatrav dark matrix (Supplementary Fig.\u0026nbsp;2), though it is observed in the petrography of all Ernestites.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eMajor and Trace elements\u003c/h3\u003e\n\u003cp\u003eThe major oxide and trace element contents of two Ernestite samples from Bhagatrav and Dholavira, as well as two laterite and two sandstone samples from Khadir Island, are presented in Supplementary Data 1. SiO\u003csub\u003e2\u003c/sub\u003e content (47\u0026ndash;61 wt%) is the highest among all oxides, with Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, FeO\u003csup\u003eT\u003c/sup\u003e, and TiO\u003csub\u003e2\u003c/sub\u003e being other major components. MnO, Na\u003csub\u003e2\u003c/sub\u003eO, and P\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e are either very low (\u0026lt;\u0026thinsp;0.1wt%) or absent, whereas K\u003csub\u003e2\u003c/sub\u003eO and MgO concentrations are minor. Bhagatrav Ernestite has lower SiO\u003csub\u003e2\u003c/sub\u003e and Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, FeO\u003csub\u003eT\u003c/sub\u003e, and TiO\u003csub\u003e2\u003c/sub\u003e than Dholavira Ernestite. The major oxide data of the laterite and sandstone samples from the Khadir Island are also presented in Supplementary Data 1. Laterites have high Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (36.7\u0026ndash;37.6 wt%), moderate SiO\u003csub\u003e2\u003c/sub\u003e (32.31\u0026ndash;32.61 wt%) and low Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (8.77\u0026ndash;8.89 wt%), TiO\u003csub\u003e2\u003c/sub\u003e (1.32\u0026ndash;1.34 wt%) contents, whereas sandstones are characterized by high SiO\u003csub\u003e2\u003c/sub\u003e (67.57\u0026ndash;68.42 wt%), moderate Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (13.26\u0026ndash;13.19), K\u003csub\u003e2\u003c/sub\u003eO (1.83\u0026ndash;1.84 wt%) and low Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (2.06\u0026ndash;2.09 wt%). Various oxides vs. SiO\u003csub\u003e2\u003c/sub\u003e diagrams plotted for Ernestites, sandstones, and laterites, along with the published data for Mesozoic sandstones\u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e,\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e and laterites-bauxites of Kutch\u003csup\u003e\u003cspan additionalcitationids=\"CR49\" citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e, are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e presents the primitive mantle (PM) normalized multi-element patterns for the Ernestite samples and those for Mesozoic rocks\u003csup\u003e\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e, and laterites of Kutch region\u003csup\u003e\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSr-Nd isotopic data for the Ernestite stones/drills and Laterites\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eType\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLocation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003csup\u003e143\u003c/sup\u003eNd/\u003csup\u003e144\u003c/sup\u003eNd\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eε\u003csub\u003eNd\u003c/sub\u003e(0)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eE-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eErnestite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBhagatrav\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.73022\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.511708\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-18.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eE-3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eErnestite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBhagatrav\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.73027 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.511703\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-18.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eE-4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eErnestite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBhagatrav\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.73087\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.511700\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-18.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3304\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDrill bit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKanmer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.72282\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.511927\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-13.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3285\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDrill bit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKanmer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.71778 \u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.511926\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-13.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eERN-KM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eErnestite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKanmer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.72207\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.511884\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-14.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eERN-DV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eErnestite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDholavira\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.712901\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.511900\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-14.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eERN-KU\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDrill bit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKhirsara\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.709991\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.511915\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-14.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKH-3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLaterite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKhadir\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.708990\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.512256\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-7.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKH-4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLaterite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKhadir\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.709551\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.512245\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-7.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKH-15-6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSandstone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKhadir\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.714940*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.511731*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-17.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKH-15-27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSandstone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKhadir\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.743439*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.511433*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e-23.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003eNote: All ratios are TIMS data except those marked with *, which are MC-ICPMS data. The average isotopic ratios and external reproducibilities determined for the international SRM-987 and JNdi-1 in TIMS, after repeated analyses over three years, are \u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr = 0.710249\u0026thinsp;\u0026plusmn;\u0026thinsp;0.000009 (2σ; n\u0026thinsp;=\u0026thinsp;14) and \u003csup\u003e143\u003c/sup\u003eNd/\u003csup\u003e144\u003c/sup\u003eNd = 0.512102\u0026thinsp;\u0026plusmn;\u0026thinsp;0.000010 (2σ; n\u0026thinsp;=\u0026thinsp;14), respectively. ε\u003csub\u003eNd\u003c/sub\u003e(0) = [(\u003csup\u003e143\u003c/sup\u003eNd/\u003csup\u003e144\u003c/sup\u003eNd)\u003csub\u003esample\u003c/sub\u003e/\u003csup\u003e143\u003c/sup\u003eNd/\u003csup\u003e144\u003c/sup\u003eNd)\u003csub\u003eCHUR\u003c/sub\u003e \u0026ndash; 1]\u0026times;10\u003csup\u003e4\u003c/sup\u003e, where CHUR\u0026thinsp;=\u0026thinsp;Chondrite Uniform Reservoir and (0) stands for present-day value.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e\n\u003ch3\u003eMineral Chemistry\u003c/h3\u003e\n\u003cp\u003eRepresentative backscattered electron (BSE) images of various phases in a polished thin section of the Kanmer Ernestite are given in Supplementary Fig.\u0026nbsp;3. Mineral compositions of different phases are provided in Supplementary Data 2. X-ray elemental maps for all three Ernestite stones (i.e., Kanmer, Bhagatrav, and Dholavira), as well as chemical spot analysis data (both by EPMA), are provided in Supplementary Figs.\u0026nbsp;3\u0026ndash;6 and Supplementary Data 2. Quartz (SiO\u003csub\u003e2\u003c/sub\u003e: 98\u0026ndash;100 wt%) of varying sizes is dispersed within the light-colored (yellow) fine matrix, which is mainly composed of aluminosilicate phases (SiO\u003csub\u003e2\u003c/sub\u003e: 40\u0026ndash;53 wt%; Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e: 40\u0026ndash;50 wt%). Although identified as mullites by XRD, the aluminosilicate matrix phases contain much higher SiO\u003csub\u003e2\u003c/sub\u003e than that mandated by stoichiometry (i.e., \u0026lt; 30 wt%; Lentz et al., 2019), therefore, we identify these phases as pseudomullites. Fe-Ti bearing phases, such as hematite (FeO: 71\u0026ndash;74 wt%) and ilmenite (TiO\u003csub\u003e2\u003c/sub\u003e: 51\u0026ndash;56 wt%), often occur as narrow patches or are finely dispersed within the light (yellow) matrix. Many hematite grains have a high TiO2 content (29\u0026ndash;40 wt%) and can thus be classified as titanohematite. The titanohematites also contain an appreciable amount of Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (5\u0026ndash;21 wt%).\u003c/p\u003e\n\u003ch3\u003eSr-Nd isotopic ratios\u003c/h3\u003e\n\u003cp\u003eResults of Sr and Nd isotopic compositions of Ernestite whole rocks and drill bits, laterites, and sandstones are provided in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The \u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr and ε\u003csub\u003eNd\u003c/sub\u003e(0) of Ernestite stones and drill bits from Kutch (Dholavira, Kanmer, and Khirsara) vary between 0.71000 and 0.72282, and -14.7 and \u0026minus;\u0026thinsp;13.9, respectively. In contrast, the Sr-Nd isotopic compositions of Bhagatrav Ernestites are more radiogenic in Sr and less radiogenic in Nd (\u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr = 0.73022 to 0.730876; ε\u003csub\u003eNd\u003c/sub\u003e(0) = -18.3 to -18.1). The drill bits from Kanmer have an identical ε\u003csub\u003eNd\u003c/sub\u003e(0) of -13.9, and one of the drill bits has almost identical \u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr as that of the Ernestite stone (0.72282 vs. 0.72207; Table\u0026nbsp;4). The laterite samples collected from the Khadir (Dholavira) have \u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr varying from 0.7089 to 0.7096, and their ε\u003csub\u003eNd\u003c/sub\u003e(0) ranges from \u0026minus;\u0026thinsp;7.7 to -7.5, whereas the sandstones have more radiogenic Sr and Nd (\u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr = 0.71494 and 0.74344; ε\u003csub\u003eNd\u003c/sub\u003e(0) = -23.5 and \u0026minus;\u0026thinsp;17.7).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn the first-ever detailed characterization, Kenoyer and Vidale\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e suggested a metamorphic origin for Ernestites based on their identification of the matrix phases as sillimanite and mullite. Mullite is a rare mineral and has only been reported from specific contact-metamorphic rocks (in metamorphosed clays) and pseudotachylites\u003csup\u003e\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e,\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e. It is also commonly observed in high-temperature ceramics and has been synthesized by heating various aluminosilicate minerals (e.g., kaolinite, kyanite, andalusite, sillimanite) at high temperatures (\u0026gt;\u0026thinsp;1100\u0026deg;C)\u003csup\u003e54\u0026ndash;57\u003c/sup\u003e. However, we identify these phases, which exhibit identical XRD spectra to mullite, as pseudomullites based on their higher SiO2 contents (\u0026gt;\u0026thinsp;40 wt%). Since mullite and pseudomullite are isostructural, all earlier studies, which relied primarily on XRD data, had incorrectly identified pseudomullite as mulite. \"Pseudomullite\" refers to a structure or phase that resembles mullite (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e) but is not the true, stoichiometric mullite. It can be formed by the decomposition of kaolinite or other aluminosilicate materials\u003csup\u003e\u003cspan additionalcitationids=\"CR58\" citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e\u003c/sup\u003e. Mullite refers to an experimentally observed solid solution series Al\u003csub\u003e4\u0026thinsp;+\u0026thinsp;2\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003eSi\u003csub\u003e2\u0026minus;2\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003eO\u003csub\u003e10\u0026minus;\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e with 0.2\u0026thinsp;\u0026lt;\u0026thinsp;\u003cem\u003ex\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.9 (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e)\u003csup\u003e\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e,\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e\u003c/sup\u003e. According to Shears and Archibald\u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e, the stoichiometric composition of synthetic mullite commonly varies between 3Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e.2SiO\u003csub\u003e2\u003c/sub\u003e (~\u0026thinsp;72 wt% Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e) and 2Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e.SiO\u003csub\u003e2\u003c/sub\u003e (~\u0026thinsp;78wt% Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e). In natural mullites, Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e substitutes Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, producing a wide range of compositions at ~\u0026thinsp;30 wt% SiO\u003csub\u003e2\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e)\u003csup\u003e\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e,\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e\u003c/sup\u003e. In contrast, stoichiometric sillimanite has ~\u0026thinsp;61 wt% Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). The aluminosilicate phase in the Ernestite matrix is pseudomullites and has higher SiO\u003csub\u003e2\u003c/sub\u003e and lower Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e than those of natural mullite or silimanite (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). Pseudomullites are not found in nature and have been shown in synthetic heating experiments to be developed as an intermediate phase during kaolinite to mullite transformation at high temperature\u003csup\u003e\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e,\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e\u003c/sup\u003e (~\u0026thinsp;1100\u0026deg;C). Therefore, the presence of pseudomullites unambiguously rules out that Ernestites are natural rocks, indicating their origin by high-temperature processing.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe Harappans artificially produced the Ernestites as the source stones for drill bits through a high-temperature heating process that could generate the pseudomullites. Further evidence for a high-temperature process is provided by the chemical composition of Fe-Ti-bearing phases, as determined by EPMA analyses. The presence of titanohematites with significant TiO\u003csub\u003e2\u003c/sub\u003e (29\u0026ndash;40 wt%) and Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (5\u0026ndash;21 wt%) suggests an extensive substitution between Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and TiO\u003csub\u003e2\u003c/sub\u003e and between Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. It is known that at temperatures below 800\u0026deg;C, only a limited solid solution between TiO\u003csub\u003e2\u003c/sub\u003e and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e is possible\u003csup\u003e\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e\u003c/sup\u003e. Similarly, in the Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e system, higher Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (up to 10 wt%) can be substituted into the hematite (Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e) structure at high temperatures only (~\u0026thinsp;1000\u0026deg;C)\u003csup\u003e\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e\u003c/sup\u003e. Therefore, higher TiO\u003csub\u003e2\u003c/sub\u003e and Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e in the titanohematite confirm a heating process (\u0026gt;\u0026thinsp;1000\u0026deg;C) in Ernestite manufacturing. It is thus apparent that the pseudomullite matrix was produced during high-temperature sintering. This provides the first geochemical evidence of sintering being used in the manufacture of Ernestites. This also successfully explains the presence of high-temperature craft objects, such as stoneware bangles\u003csup\u003e\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e,\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e\u003c/sup\u003e, steatite beads\u003csup\u003e\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e\u003c/sup\u003e, and furnaces\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e,\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e, at the Harappan sites. The presence of detrital quartz grains, ilmenite, hematite, zircon, and rutile suggests that the raw materials used to make the Ernestites are natural, even though the manufacturing process was artificial.\u003c/p\u003e \u003cp\u003eLaw\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e suggested tonstein as the only raw material for Harappan Ernestites. He attributed the coarser (up to 100 \u0026micro;m) subhedral quartz or cristobalite grains (detected in his BSE images) to the recrystallized free silica (released during heating) and zircon to a magmatic origin. He further proposed that the raw materials for the Ernsitites (i.e, tonsteins) were sourced from local/regional sources (i.e., Kutch). Tonsteins are hard and compact kaolinite-altered volcanic ash layers, generally found in coals and associated sediments\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. These often contain magmatic quartz and zircon\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e,\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e\u003c/sup\u003e. However, microtextural characteristics of these constituent minerals suggest that zircon, quartz, ilmenite, and rutile in Ernestites are essentially detrital. Therefore, tonstein is ruled out as Ernestite's raw material. Additional evidence against using tonsteins for Ernestites comes from the presence of non-radiogenic Nd in the Ernestites (ε\u003csub\u003eNd\u003c/sub\u003e(0) \u0026lt; -14), because all ash beds in Kutch are linked to the Deccan Traps\u003csup\u003e\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e, which contain more radiogenic Nd (ε\u003csub\u003eNd\u003c/sub\u003e(0) \u0026gt; -11, Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). Besides, our Ernestite samples contain sand-sized detrital quartz and ilmenite grains in contrast to a claystone/tonstein that usually contains clay-sized grains (\u0026le;\u0026thinsp;2\u0026micro;m).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe detrital quartz grains' size and moderately sorted nature suggest using coarser raw materials, such as sandstones, which were likely pounded into sand/silt-sized particles before being processed for sintering. It is possible that the Fe-Ti phases (hematite, titanohematite, ilmenite, and rutile) observed in the Ernestites also originated from the sandstones, as sandstones generally contain such heavy minerals. However, our Ernestites appear to exhibit mixing trends between Mesozoic sandstones and laterites-bauxites of the Kutch region in various oxide vs. SiO\u003csub\u003e2\u003c/sub\u003e plots (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Trace element patterns (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) also suggest that such a mixture is necessary to explain the chemistry of the Ernestites. Besides, high contents of Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (\u0026gt;\u0026thinsp;20 wt%) and high field strength elements (e.g., Sc, V, Cr, and Co) in Ernestites cannot be achieved by the sandstones of the Kutch alone. Therefore, a second end-member, containing Fe-Ti minerals but low in alkali elements, is needed to explain the Ernestite chemistry, and the laterites of Kutch, derived from the mafic volcanic rocks of the Deccan Traps, fit the bill. The Paleocene to Eocene lateritic deposits in western Kutch (Matanomadh Formation) and Saurashtra (Jamnagar) contain both Al-rich (gibbsite, kaolinite) and Fe-rich (goethite, hematite, ilmenite-rich) phases and are depleted in alkalis\u003csup\u003e\u003cspan additionalcitationids=\"CR49\" citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e, and have the required characteristics of this raw material. Although we discard claystone as the sole raw material, we do not deny its possible use in combination with sandstone and laterite for Ernestite manufacturing.\u003c/p\u003e \u003cp\u003eSince kaolinite is a common mineral in laterites, it could have decomposed and undergone subsequent chemical and structural changes to form the pseudomullite matrix during the sintering process. The free (amorphous) silica released during the heating of pure kaolinite recrystallizes as cristobalite upon further heating (to ~\u0026thinsp;1350\u0026deg;C)\u003csup\u003e\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e\u003c/sup\u003e and when kaolinite is heated with alumina-bearing material (e.g., bauxite, aluminum fluoride, aluminum hydroxide), free silica formation is prohibited\u003csup\u003e\u003cspan additionalcitationids=\"CR69\" citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e\u003c/sup\u003e. We suspect that during the sintering process carried out by the Harappans, the free silica (SiO\u003csub\u003e2\u003c/sub\u003e) formation was suppressed by the presence of gibbsite (Al(OH)\u003csub\u003e3\u003c/sub\u003e) in the laterite. Moreover, gibbsite undergoes thermal decomposition to boehmite (AlO.OH) at 200\u0026deg;C, which transforms into a transitional alumina (α- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e) phase at 500\u0026deg;C\u003csup\u003e\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e71\u003c/span\u003e,\u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e\u003c/sup\u003e. We suspect that the Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e in the titanohematite structure was sourced from gibbsite (lateritic) in the mixture during the α-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e stage. Since the results of our study point to a maximum temperature of 1100\u0026deg;C for the sintering process, the cristobalites observed by Law\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e likely represent a higher temperature or longer heating process.\u003c/p\u003e \u003cp\u003eSimilar \u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr and ε\u003csub\u003eNd\u003c/sub\u003e(0) of Ernestite stone and drill bits from Kanmer genetically link the drill bits to the stone. Although it has been well established that Ernestite stones are the raw materials for long and constricted cylindrical drill bits\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e, their isotopic similarity is the first-ever chemical evidence for the same. Because of the sheer number of Ernestite stones and drill bits from Dholavira, Law\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e speculated that the raw materials for the stones came from either the island itself (i.e., Khadir) or the Kutch region of Gujarat. However, our geochemical data (Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) support a regional sourcing of the raw materials. The sandstones and laterites of Kutch appear to have been the primary sources of the raw materials for the Ernestites. In search of more robust evidence for this geological provenance hypothesis, we make use of the Sr-Nd isotopic compositions of Ernestites and their potential source rocks (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e; Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). Although, the ε\u003csub\u003eNd\u003c/sub\u003e and \u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr compositions of the Ernestites plot well within the compositional field of the Mesozoic sandstones of Kutch, they can be explained by a two-component mixing between the sandstones and laterites of Khadir (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). The isotopic compositions of laterites of Khadir, which are developed over volcanic ash of Deccan Traps fall well within the field of the Deccan Basalts, which suggests that other lateritic horizons in the Kutch and Saurashtra region, developed over Deccan Trap rocks could also have served as sources for the raw material for Ernestites. The mixing model suggests 55\u0026ndash;60% contribution from these end-members to the isotopic compositions of most of our samples; however, those from Bhagatrav (in south Gujarat) require\u0026thinsp;~\u0026thinsp;80% contribution from the sandstones. Therefore, we infer that the Harappans used laterite from different weathered (Deccan) horizons and sand from Mesozoic sandstones from Kutch to manufacture Ernestites.\u003c/p\u003e \u003cp\u003eWe make the following conclusions based on our investigation of Ernestites, the parent material for the unique constricted drill bits of the Harappan Civilization, using petrographic, mineralogical, geochemical, and Sr-Nd isotopic techniques.\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eStone drill bits have been isotopically fingerprinted to the Ernestites, confirming their genetic link.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe Ernestites consist of medium sand to fine silt detrital quartz, hematite, ilmenite, zircon, and rutile welded together in a fine-grained aluminosilicate matrix/groundmass.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eErnestites\u0026rsquo; texture (larger mineral grains and their detrital nature), and its whole-rock Nd isotopic composition (ε\u003csub\u003eNd\u003c/sub\u003e(0) \u0026gt; -11) rule out the use of tonstein flint as a raw material.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe aluminosilicate matrix/groundmass phase has been chemically identified as pseudomullite, though its XRD spectrum is similar to mullite.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe presence of pseudomullites, with high SiO\u003csub\u003e2\u003c/sub\u003e contents (\u0026gt;\u0026thinsp;40 wt%), unambiguously makes Ernestites artificial, with supporting evidence from the significant substitution of Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and TiO\u003csub\u003e2\u003c/sub\u003e in hematites. These data also suggest a high temperature (reaching 1100\u0026deg;C) synthesis of Ernestites.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eMineralogy, texture, and mineral chemistry suggest Ernestites were manufactured through a high-temperature sintering process involving sand and clay-bearing raw materials.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eMajor and trace elements and Sr-Nd isotopic data point to the likelihood of the raw materials' regional provenance (sandstones and laterites of Kutch).\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eAll our findings suggest that Ernestites were likely made in the Harappan centres of Gujarat, India, and the Ernestite-based drilling technology was exclusive to this civilization.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e"},{"header":"Declarations","content":" \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare no competing interests related to this work.\u003c/p\u003e \u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eJ.S.R and A.C. conceived the study. A.K.K., Y.S.R., J.S.K., and S.V.R .supplied samples. A.C., M.K.M., B.G.G., N.S., and G.N.S.S.B. conducted the analytical work. M.K.M., G.N.S.S.B., A.C., and J.S.R. interpreted the data. J.S.R. secured the project\u0026rsquo;s funding, and all authors contributed to the writing.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eJSR thanks the Physical Research Laboratory, Ahmedabad, India, for funding. The authors acknowledge the laboratory support of Sneha Mukherjee of NCESS and Jitender Kumar of PRL.\u003c/p\u003e\u003ch2\u003eData Availability Statement\u003c/h2\u003e \u003cp\u003eAll data generated for this study are in the tables in the manuscript and the supplementary files.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eRamesh S. The Indus Valley Civilisation: 3000 BC to 1600 BC. In: Ramesh S, editor. 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An Introduction to the Rock-Forming Minerals. Essex, England: Longman Scientific and Technology; 1992.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePracchia S, Vidale M, Volpicelli O. The Archaeological Context of Stoneware Firing at Mohenjo-Daro. East West. 1993;43:23\u0026ndash;68.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVidale M. The Archaeology of Indus Crafts: Indus Craftspeople and Why We Study Them. Rome: Istituto Italiano per lAfrica el\u0026rsquo;Oriente; 2000.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDe Barth\u0026eacute;lemy B, Bouquillon A. Steatite working at Mehrgarh during the Neolithic and Chalcolithic periods: quantitative distribution, characterization of material and manufacturing processes. 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Chem Geol. 1995;120:223\u0026ndash;53.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSimonetti A, Goldstein SL, Schmidberger SS, Viladkar SG. Geochemical and Nd, Pb, and Sr isotope data from Deccan alkaline complexes\u0026mdash;inferences for mantle sources and plume\u0026ndash;lithosphere interaction. J Petrol. 1998;39:1847\u0026ndash;64.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePaul DK, Ray A, Das B, Patil SK, Biswas SK. Petrology, geochemistry and paleomagnetism of the earliest magmatic rocks of Deccan Volcanic Province, Kutch, Northwest India. Lithos. 2008;102:237\u0026ndash;59.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSheth HC, et al. Geology and geochemistry of Pachmarhi dykes and sills, Satpura Gondwana Basin, central India: problems of dyke-sill-flow correlations in the Deccan Traps. 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Sr and stable Ca isotopic study of carbonatites and associated silicate rocks from the ~\u0026thinsp;65 Ma old Ambadongar carbonatite complex and the Phenai Mata igneous complex, Gujarat, India: Implications for crustal contamination, carbonate recycling, hydrothermal alteration and source-mantle mineralogy. Lithos. 2019;326\u0026ndash;327:572\u0026ndash;85.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChandra J, Paul D, Stracke A, Chabaux F, Granet M. The Origin of Carbonatites from Amba Dongar within the Deccan Large Igneous Province. J Petrol. 2019;60:1119\u0026ndash;34.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChatterjee A. Provenance of late quarternary continental sediments in western India insight from trace element and isotope geochemistry. Maharaja Sayajirao University of Baroda; 2017.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"npj-heritage-science","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"hsci","sideBox":"Learn more about [Heritage Science](http://heritagesciencejournal.springeropen.com)","snPcode":"40494","submissionUrl":"https://submission.nature.com/new-submission/40494/3","title":"npj Heritage Science","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6780927/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6780927/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAdvancements in stone bead technology, particularly in drilling techniques, emerged during the Indus Valley (Harappan) civilization. Long-constricted cylindrical drill bits, made from a unique stone called Ernestite, were a distinctive feature of this culture. The origin of Ernestite is a mystery due to the lack of a natural analogue and an unknown manufacturing process. This study presents a mineralogical and geochemical investigation of Ernestite stones and drill bits from several Harappan and contemporaneous sites in Gujarat, India, to uncover their origin. The isotopic ratios of Sr and Nd link the drills to the Ernestites. The texture and presence of pseudo-mullite (SiO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;\u0026gt;\u0026thinsp;40 wt%) with high Al-Ti-bearing hematite suggest that Ernestites are synthetic, created through a sintering process at ~\u0026thinsp;1100\u0026deg;C. An abundance of sand to silt-sized detrital quartz, along with Fe-Ti-Zr-rich minerals, indicates the use of crudely powdered sandstones and laterites as raw materials, with geochemical ties to regional sources.\u003c/p\u003e","manuscriptTitle":"Origin of the Harappan Ernestites: Geochemical Insights into Provenance and Fabrication","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-20 16:29:47","doi":"10.21203/rs.3.rs-6780927/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-07-14T21:20:13+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-11T16:32:33+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-05T15:39:09+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-03T09:07:17+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"226545261050853711237240391127146292380","date":"2025-06-22T09:47:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"72860227828458056752899329953271870992","date":"2025-06-21T11:38:28+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"165246285260315160378433133458578893044","date":"2025-06-19T14:33:15+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-18T16:01:05+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-11T21:44:36+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-10T09:07:24+00:00","index":"","fulltext":""},{"type":"submitted","content":"npj heritage science","date":"2025-06-10T09:01:51+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"npj-heritage-science","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"hsci","sideBox":"Learn more about [Heritage Science](http://heritagesciencejournal.springeropen.com)","snPcode":"40494","submissionUrl":"https://submission.nature.com/new-submission/40494/3","title":"npj Heritage Science","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"918049ae-1177-4660-b885-6cf1d4792912","owner":[],"postedDate":"June 20th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-01T16:01:51+00:00","versionOfRecord":{"articleIdentity":"rs-6780927","link":"https://doi.org/10.1038/s40494-025-02147-2","journal":{"identity":"npj-heritage-science","isVorOnly":false,"title":"npj Heritage Science"},"publishedOn":"2025-11-28 15:56:56","publishedOnDateReadable":"November 28th, 2025"},"versionCreatedAt":"2025-06-20 16:29:47","video":"","vorDoi":"10.1038/s40494-025-02147-2","vorDoiUrl":"https://doi.org/10.1038/s40494-025-02147-2","workflowStages":[]},"version":"v1","identity":"rs-6780927","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6780927","identity":"rs-6780927","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}