XRD, SEM Characterisation and Economic Potentials of Volcaniclastic-Derived Clays from Ediki, Mungo Formation, SW Cameroon

XRD, SEM Characterisation and Economic Potentials of Volcaniclastic-Derived Clays from Ediki, Mungo Formation, SW Cameroon | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article XRD, SEM Characterisation and Economic Potentials of Volcaniclastic-Derived Clays from Ediki, Mungo Formation, SW Cameroon Enerst Tata¹, Kevin Ijunghi Ateh, Cheo Emmanuel Suh, Elisha Mutum Shemang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9147332/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract The Cretaceous Mungo Formation in Ediki, situated in southwestern Cameroon, is characterised by sandstone, siltstone, and carbonates, overlain by pyroclastics and undifferentiated mafic rocks. Clayey occurrences are ubiquitously sandwiched within the sandstones. To determine the clay mineral diversity and commercial applicability, eleven clay samples were obtained through scooping and analysed by XRD and SEM methods. XRD results show kaolinite (NK1, NK2, NK4, NK6, NK7, NK8), halloysite (NK3, NK5, NK11), and illite (NK9) as major clay phases, while montmorillonite, feldspar, and quartz are associated with the clay. Magnetite, hematite, and ilmenite occur as impurities. Gibbsite is recorded in one sample (NK10). SEM reveals that the kaolinites are flat, plate-like, and lotus-like; halloysite is spongy, rod-like, and pseudo-spheroidal, while illite is scallop-shaped. The gibbsite sample is stalactitic. The clays are derived from the decomposition of the pyroclastics, ash, and ultramafic and mafic rocks. The iron oxide impurities are from mafic rocks, while quartz is derived from sandstone and siltstone. The occurrence of gibbsite indicates deep weathering in a warm, humid climate. Kaolinite and illite have potential use in ceramics, paper, and as components in cosmetics and toothpaste; montmorillonite and halloysite, as drilling fluids, catalysts, and adsorbents for environmental remediation, drug delivery, and to create stronger nanocomposites. XRD SEM Clay Cretaceous Ediki Cameroon Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction Clay minerals are economically important as development minerals, especially in developing nations, by virtue of their wide applications in industry and pharmaceutics and have been mined in world-class deposits such as Cornwall and Cape York Peninsula in England and Australia, respectively [ 1 ]. These minerals are hydrous aluminosilicates that have particle sizes less than 2 µm. They are mostly plate-like in shape and become plastic when wet but stone hard when dry. Their formation is usually through surface weathering, precipitation, low-temperature metamorphism, and diagenesis [2 − 4]. Their formation depends on climatic conditions and overall soil development [ 5 ], with rock composition also playing a crucial role [ 6 ]. Tropical conditions with high rainfall, warm temperatures, and high biological activity accelerate chemical weathering, which creates environments that typically produce clays like vermiculite, illite, kaolinite, halloysite, and montmorillonite, along with non-clay minerals such as gibbsite, hematite, and goethite. Cameroon's geographical and geological setting favours widespread clay deposit formation [7 − 9]. Numerous deposits have been reported in many areas in Cameroon, with extensive characterisation of their nature and geochemical properties (e.g., [ 10 , 11 ]. These materials have been valorised primarily for ceramic production, including bricks, tiles, and fine porcelain [12 − 14]. Southwestern Cameroon hosts ubiquitous clay occurrences that remain poorly investigated regarding their mineralogical characterisation. Previous work in the study area includes studies of kaolin profiles in the Mungo Formation [ 15 ] and characterisation of basement-derived clays in south-central Cameroon [ 10 , 16 ]. This study aims to document the mineral assemblage of the Ediki clayey occurrences, construe their genesis, and highlight potential industrial applications using X-ray diffractometry and scanning electron microscopy. 2. Study Site 2.1. Geographical situation Ediki is a locality in Kumba 3 Sub-Division of the South West Region of Cameroon (Fig. 1 (a-d ). It is bordered to the north by Mabonji, to the south by Mbalangi, to the east by the Mungo River, and to the west by Pete. The climate is tropical, with distinct rainy (April-September) and dry (October-March) seasons. The mean temperature is 25°C, with rainfall ranging from 2085 to 9086 mm and peaking in June and July [ 17 , 18 ]. This high rainfall reflects Ediki's position in a hyper-humid coastal belt. The area is drained by the north-south flowing Mungo River and its dendritic tributaries. The topography is gentle, averaging 111 meters above sea level. 2.2. Geological setting of the study area Geologically, Ediki forms part of the Cretaceous-Quaternary Douala sub-sedimentary basin, which is the northwestern extension of the west-central coastal province [ 19 ]. The local rocks belong to the Mungo Formation, which overlies the Mundeck Formation. The Mungo Formation comprises sandstone, shale, limestone, marl, silty clays, and siltstone. Clay occurrences are hosted within Upper Cretaceous (Turonian-Cenomanian) sandstones of this formation, which are overlain by recent pyroclastics and basaltic boulders. Within the study area, discontinuous shale outcrops appear along intermittent stream beds, while fossiliferous limestone occurs in central Ediki and along the Mungo riverbanks. Recent alluvium deposits towards the east, particularly along riverbanks, overlie isolated undifferentiated basaltic volcanic rocks. A hiatus separates these recent deposits from the underlying Mungo Formation transitional sequence of shale, limestone, and fine-grained sandstone characteristic of a low-energy coastal environment. 3. Methods 3.1. Sampling and Sample Preparation Eleven clay samples were collected judgmentally from outcrops along the main road and railway cuttings. The selection criteria included colour variation, texture, clay horizon thickness, and the absence of visible contamination. The samples were collected vertically at intervals determined by outcrop extent. The clay occurrences sampled were closely associated with decomposed pyroclastics that overlay the cretaceous sandstones of the Mungo Formation of the Douala sub basin. The samples were then wrapped in labelled bags and transported to the Geology Laboratory of the University of Buea. At the laboratory, the samples were air-dried and crushed using an agate mortar and pestle. The crushed material was sieved and the clay fraction obtained after treatment in distilled water with caustic soda added for effective particle separation to obtain the < 2 µm. Four hundred grams of each clay fraction were sent to the Department of Earth and Environmental Sciences at the Botswana International University of Science and Technology (BIUST) for XRD and SEM analyses. 3.2. X-ray Diffractometry (XRD) Analysis No pre-treatment was applied to preserve all mineral phases within this size fraction. All the samples were subjected to ethylene glycol treatment for proper clay characterisation. Major mineral composition was determined semi-quantitatively on bulk fractions at the University of Botswana, Gaborone, using a Philips PW1710 X-ray diffractometer. The instrument utilized monochromatic Cu Kα radiation and an automatic divergence slit at 40 kV and 35 nA. Randomly oriented powder samples were mounted in aluminium holders and scanned from 5° to 90° 2θ with a step size of 0.02°, a scan speed of 1.2°/min, and a 0.5 s count time. Minerals were identified via multiple peak matches using the MacDiff software and its integrated mineral database. Diffractograms were interpreted using X'PERTR Data Collector software. 3.3. Scanning Electron Microscopy (SEM) Analysis SEM imaging was performed using a Philips XL30 Environmental Scanning Electron Microscope equipped with an energy-dispersive spectrometer. The clay fraction of each sample was mounted on aluminium stubs with carbon-coated conductive glue, then viewed and photomicrographed. SEM was used solely to characterise particle morphology; no chemical analyses from EDS are reported here. 4. Results 4.1. XRD Analysis of Clay Mineral Fraction XRD analyses identified kaolinite, halloysite, illite, gibbsite, montmorillonite, quartz, feldspar, ilmenite, magnetite, and hematite as the various mineral phases (Table 1 ). Kaolinite is the dominant clay mineral in the area, occurring as the predominant phase in six samples (NK1, NK2, NK4, NK6, NK7, NK8). Magnetite and hematite occur as traces in most samples except NK1 and NK3. Halloysite is the major mineral in three samples (NK3, NK5, NK11), while illite and gibbsite (non-clay mineral) dominate samples NK9 and NK10, respectively. Ilmenite occurs as traces in samples NK2, NK3, and NK9. Quartz is an insignificant phase, occurring in trace amounts in only two samples (NK3, NK10). Montmorillonite is also insignificant, appearing only in trace amounts in NK1. Feldspar, a non-clay mineral, appears in trace amounts in four samples (NK1, NK2, NK3, NK4). Table 1 Mineral phases identified at the Ediki clayey occurrences by XRD analyses SAMPLE GROUP SAMPLE NUMBER / COORDINATES COMPOUND NAME/DESCRIPTION CHEMICAL FORMULA KAOLINITE (Fig. 2 ) NK1: 550901E 501049N Montmorillonite-22A Na 0.3 (Al, Mg) 2 Si 4 O 10 (OH) 2 ·8H 2 O Iron (III) oxide Fe 2 O 3 Halloysite (residual surrounding kaolinite peaks) Al 2 O 3 ·2SiO 2 ·xH 2 O Kaolinite (major mineral with minimal halloysite and feldspar) Al 2 Si 2 O 5 (OH) 4 NK2 550974E 501243N Magnetite Fe 2.75 Ti 0.2 5O 4 Ilmenite FeTiO 3 Magnetite Fe 3 O 4 Kaolinite (Prominent peaks) Al 2 Si 2 O 5 (OH) 4 Feldspar (at 20 theta) K 0.47 Na 0.43 Ca 0.10 Al 1.1 Si 2.9 O 8 NK4 551404E 501427N Magnetite Fe 0.65 Fe 1.81 Mg 0.42 Al 0.1 Ti 0.03 O 4 Halloysite Al 2 O 3·2 SiO 2 ·2H 2 O Feldspar Kaolinite (two highest peaks) Al 2 Si 2 O 5 (OH) 4 Iron (III) oxide Fe 2 O 3 NK6 551587E 501820N Iron (III) oxide (noisy peaks) Fe 2 O 3 Magnetite (Noisy peaks) Fe 3 O 4 Hematite (Noisy peaks) Fe 2 O 3 Illite (small peaks in between) 2K 2 O 0·3 MgO·Al 2 O 3·24 SiO 2·12 H 2 O Kaolinite (three major peaks) Al 2 Si 2 O 5 (OH) 4 NK7 551587E 501820N Hematite (small noisy peaks) Fe 2 O 3 Magnetite (Small noisy peaks) Fe 2.946 O 4 Kaolinite (3 major peaks) Al 2 Si 2 O 5 (OH) 4 Feldspar (1st small peak) NK8 551706E 501696N Magnetite (Noisy peaks) Fe 2.929 O 4 Halloysite (high peak at the end) Al 2 O 3 ·2SiO 2 ·2H 2 O Feldspar (Noisy peaks) (K, Na)(Si 3 Al)O 8 Illite (peak at 53.5) 2K 2 O 0·3 MgO·Al 2 O 3·24 SiO 2·12 H 2 O Kaolinite (2 highest peaks) Al 2 Si 2 O 5 (OH) 4 HALLOYSITE (Fig. 3 ) NK3 551456E 501180N Feldspar and quartz (smaller peaks) (K, Na)(Si 3 Al)O 8 , SiO 2 Halloysite (2 high peaks) Al 2 O 3 ·2SiO 2 ·2H 2 O Illite (last peak) 2K 2 O·3Mg·Al 2 O 3 ·24SiO 2 ·12H 2 O NK5 551315E 501815N Feldspar (K, Na)(Si 3 Al)O 8 Halloysite (Highest peak) Al 2 O 3 ·2SiO 2 ·xH 2 O Kaolinite (peak to its right) Al 2 Si 2 O 5 (OH) 4 Magnetite high Fe 2.945 O 4 Iron (III) oxide Fe 2 O 3 NK11 552289E 501140N Hematite Fe 2 O 3 Magnetite Fe 3 O 4 Halloysite Al 2 O 3·2 SiO 2 ·xH 2 O Illite 2K 2 O 0·3 MgO·Al 2 O 3 ·24SiO 2 ·12H 2 O ILLITE (Fig. 4 ) NK9 552403E 501630N Magnetite Fe 3 O 4 Halloysite Al 2 O 3 ·2SiO 2 ·2H 2 O Feldspar (K, Na)(Si 3 Al)O 8 Illite (Prominent peaks) KAl 2 (Si 3 AlO 10 )(OH) 2 ilmenite FeTiO 3 GIBBSITE (Fig. 4 ) NK10 552036E 500491N Magnetite (Noisy peaks) Fe 3 O 4 Iron-magnesium compounds (noisy peaks) Mg 0.208 Fe 0.955 Ti 0.833 O 3 Quartz (peak just before gibbsite) SiO 2 Gibbsite (Highest peak) Al(OH) 3 Halloysite (Next peaks in height) Al 2 O 3 2SiO 2 ·x H 2 O These mineral phases can be grouped into four dominant categories: kaolinite, halloysite, illite, and gibbsite. The kaolinite group shows several associations: NK1, NK4, and NK8 contain kaolinite with halloysite, montmorillonite, feldspar, and magnetite; NK2 and NK7 have kaolinite with feldspar, magnetite, and ilmenite; NK6 contains kaolinite with illite and magnetite. Kaolinite peak intensities range from approximately 80 to over 150 counts, with halloysite and feldspar peaks in these samples below 50 counts. As seen in Table 1 , the halloysite group includes NK3, NK5, and NK11 (Fig. 3 ), with halloysite peaks exceeding 150 counts. NK5 shows halloysite with kaolinite and magnetite; NK11 contains halloysite with illite, magnetite, and hematite; NK3 includes halloysite with feldspar, ilmenite, and quartz. The illite phase is represented by sample NK9, showing illite with halloysite, magnetite, and feldspar. The gibbsite phase is sample NK10, containing gibbsite with quartz, halloysite, and magnetite (Fig. 4 ). Illite XRD counts exceed 80, while gibbsite counts exceed 150. 4.2. Clay Structure and Morphology 4.2.1. Kaolinite Structure and Morphology Kaolinite has a 1:1 layer structure with Al³⁺ in octahedral sites and Si⁴⁺ in tetrahedral sites (Fig. 5 ). The electrically neutral layers are held together by hydrogen bonding between basal oxygens and adjacent hydroxyl groups. This structure in its form limits isomorphous substitution, resulting in a nearly fixed chemical formula of Al ₂ Si ₂ O ₅ (OH) ₄ . Kaolinite in these samples displays various morphologies (Fig. 6 ). NK1 and NK2 show flat, plate-like crystals, while NK4, NK6, and NK7 exhibit aggregated pseudohexagonal, stacked crystal flakes. NK6 and NK8 contain loose pseudo-vermiform flakes. Most kaolinite particles lack parallel orientation and show face-to-edge fluctuations (NK1, NK2, NK7). This platelet morphology contributes to the material's plasticity, which is important for ceramic applications. 4.2.2. Halloysite Structure and Morphology Halloysite has a layered structure like kaolinite but with water molecules separating the 1:1 layer (Fig. 5 ). This higher water content makes it less stable, allowing transformation to kaolinite over time. SEM images reveal distinct halloysite morphologies, which are varied in the Ediki area (Fig. 7 ). NK3 shows spongy hydroid shapes, NK5 exhibits loosely stacked pseudo-spheroidal platelets, and NK11 reveals rod-like or tubular structures. This tubular morphology is particularly interesting for nanotechnology applications such as nano containers. 4.2.3. Illite and Gibbsite Structure and Morphology The illite sample (NK9) displays scalloped edges, loose platelets with irregular elongated spines, and a cornflake texture with tightly packed crystals. The gibbsite sample (NK10) shows a typical crystalline structure with stalactite-like aggregates (Fig. 8 ). 5. Discussion 5.1. Genetic Significance of Ediki Clays generally form through silicate mineral instability, particularly feldspars, occurring in supergene weathering crusts, soils, continental and marine deposits, volcanic deposits, geothermal fields, altered wallrock, and low-grade metamorphic rocks [ 2 ]. Their formation depends on climate-rock interactions, which directly influence clay properties. Clay deposits are classified as primary (formed in situ) or secondary (sedimentary origin). Ideal conditions for kaolinitic clay formation include high rainfall, warm temperatures, lush vegetation, low relief, and high groundwater tables [ 20 , 21 ]. Field observations at Ediki show gradational contacts between clay concentrations and the overlying laterite cover and the pyroclastics, with clays near presumed volcanic parent rocks and pyroclastics. This supports in-situ formation through decomposition of the dominant pyroclastic deposits rather than the allochthonous hypothesis. The XRD analysis confirms kaolinite, halloysite, illite, and gibbsite as main constituents, with montmorillonite, feldspar, and iron oxides as accessories like other deposits in the coastal regions of Cameroon [ 15 ]. The Ediki clays likely formed from weathering of Mount Cameroon volcanic and volcaniclastic rocks, including basalts and ankaramite. They differ from Cretaceous kaolins of the Douala Sub-Basin, which contain kaolinite, smectite, and illite as major phases [ 22 ]. The clays are of supergene origin due to the absence of hydrothermal indicator minerals like pyrite that would suggest limited hydrothermal influence in contrast to the hydrothermally influenced deposits like Balengou n[ 23 ]. The parent rocks that decomposed are the same as those of other clay deposits along the Cameroon Volcanic Line [ 11 , 24 ]. However, Ediki clays differ from northern Cameroon's quartz-rich smectitic clays formed under Sudano-Sahelian conditions [ 25 ]. Traces of montmorillonite in the clay materials from Ediki indicate chemical decomposition of volcanic ash rich in plagioclase feldspar. Halloysite typically forms from ultramafic rocks, volcanic glass, and pumice, often alongside kaolinite [ 20 , 26 ]. Illite within the Ediki deposit is derived from kaolinite chemical alteration under deep burial conditions through loss of interlayer water. The iron oxides point to a volcanic protolith, like clays reported from Mount Bana [ 27 ]. Gibbsite and illite in the Ediki area are likely formed at different depths, with gibbsite at shallow levels and illite at greater depths. Gibbsite forms through prolonged tropical weathering of aluminium-bearing minerals like feldspars [ 28 ]. Its presence indicates advanced weathering where silicon has been removed from kaolinite or halloysite, typically occurring in ferrosols where intense weathering prevents neo-feldspar formation [ 29 ]. The Ediki clay assemblage shows both similarities and differences with other Cameroonian deposits. Unlike smectite-rich northern clays [ 25 , 30 ], Ediki clays are dominated by kaolinite-halloysite with very minor smectite content. They share similarities with other volcaniclastic-derived clays along the CVL [ 11 ] but differ from hydrothermally influenced Balengou deposits [ 23 ]. This mineralogical diversity across Cameroon reflects variations in parent rock composition and weathering conditions. 5.2. Commercial Applicability of the Ediki Clay The economic value of clay is infrequently determined by its bulk chemical composition alone; rather, it is a direct function of its mineralogical structure and physicochemical properties Kaolinites have a 1:1 layer structure that does not expand, making it physically stable and resistant to high temperatures. The Ediki clay assemblage, characterised by dominant kaolinite and halloysite with subsidiary illite, trace quartz and feldspar, and very low montmorillonite content, presents several industrial opportunities. The economic application of the Ediki clay will be enhanced through further use of chemical characterisation methods including XRF and geotechnical characterisation to determine the Atterberg’s limits, shear strength index, volume change potential, hydraulic conductivity, and the natural moisture content to definitively determine the economic value. The XRD and SEM results permits a preliminary economic assessment of the Ediki deposit and paves the way for further research and resource definition. 5.3.1. Suitability for Ceramics Clays have extensive industrial applications, including building bricks, water filters, rubber, pharmaceuticals, and personal care products. Kaolinite-rich clays are the most abundant and widely used worldwide. Ediki's kaolinite is suitable for ceramic fabrication due to its strength, plasticity, and refractoriness. The specific mineral association at Ediki, mainly kaolinite, halloysite, illite, and gibbsite with trace quartz, is appropriate for ceramic applications. Kaolinite provides essential strength, plasticity, and refractoriness. Illite promotes vitrification, which densifies final products. Quartz prevents cracking, shrinking, and warping while providing a uniform shape during sintering at 850–1050°C for fired bricks and tiles [ 31 ], with small amounts also improving water absorption properties. The very low smectite (montmorillonite) content is advantageous for ceramic building materials, as high smectite content can cause excessive shrinkage and cracking. 5.3.2. Potential for Nanotechnology (Halloysite) Beyond traditional uses, clays are increasingly employed in advanced materials and composites, including engineered ceramics, lightweight aggregates, hybrid metallo-ceramic composites, geopolymers, adsorbents, and pharmaceutical carriers [ 32 ]. Halloysite, a kaolin-group mineral, is primarily used in ceramics, but its applications in other industries are expanding due to unique properties [ 26 ]. Its suitability for nanotechnology depends on purity and the properties of its nano-sized tubular structure. Naturally occurring halloysite holds promise in nanotechnology due to unique physicochemical properties derived from its tubular morphology. With low global reserves, natural halloysite offers an economical alternative to synthetic nanomaterials. The association of halloysite with kaolinite at Ediki enhances the economic prospects of these materials. 5.3.3. Other Potential Uses Montmorillonite, though present only in trace amounts in one sample, has diverse applications, including oil drilling muds, soil additives for water retention, petroleum refining catalysts [ 33 ], pharmaceuticals, animal feed, desiccants, cosmetics, paper, and food industries. However, its trace occurrence at Ediki suggests these applications would require blending with higher-grade material. Gibbsite, though not a clay mineral, influences soil management in the area. It contributes to soil aggregate stability, reducing erosion susceptibility, and strongly adsorbs phosphorus, which can limit plant availability. Gibbsite also promotes soil particle flocculation, influencing soil structure and water movement. 6. Conclusions The Ediki area contains sandstones, siltstone, basalts, and recent pyroclastics of the Mungo Formation, with shale and limestone along riverbanks. Field observations support in-situ clay formation through intense tropical weathering of pyroclastics and undifferentiated mafic to ultramafic rocks. XRD reveals Ediki clays are predominantly kaolinite, halloysite, and illite. Kaolinite dominates six samples (NK1, NK2, NK4, NK6, NK7, NK8), halloysite dominates three (NK3, NK5, NK11), illite dominates NK9, and gibbsite dominates NK10. Minor components include trace montmorillonite (NK1 only), ilmenite, magnetite, hematite, quartz, and feldspar. The mineral assemblage indicates formation through intense tropical weathering of pyroclastics, basalts, and associated volcaniclastic rocks. The presence of gibbsite signifies advanced leaching under warm, humid conditions. The absence of hydrothermal indicator minerals suggests supergene weathering without significant hydrothermal influence. Kaolinite and halloysite are valuable for ceramics and pottery. Very low smectite content benefits ceramic applications. Tubular halloysite suggests the potential for higher-value applications in nanotechnology, adsorbents, and advanced composites. The overall assemblage is suitable for traditional ceramic building materials. Declarations Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors declare no competing interests Author Contribution Enerst Tata: conceptualization, methodology, data curation, and writing of original draft. Ateh K. Ijunghi: visualization, writing- review & editing, validation. Cheo E. Suh and Elisha M. Shemang: Review & editing, validation of manuscript. Acknowledgements This contribution received funding from the International Union of Geological Sciences (IUGS) under its "Resourcing Future Generations" programme, coordinated by Prof. C.E. Suh at the University of Buea, Cameroon. 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Clay Miner. 2013a;48:655–62. http://doi:10.1180/claymin.2013.048.4.18 . Kamga R, Njoya A, Nkoumbou C, Tchoua FM. (2001). Mineralogical and physico-chemical characteristics of the swelling clay of Sabga (NW Cameroon). In: Proceedings of the First Conference on the Valorization of Clay Materials in Cameroon, Yaoundé, pp. 31–43. Durgut E, Çinar M, Özdemir O. An overview of Halloysite Mineral. Sci Min J. 2023;62(4):175–82. https://doi.org/10.30797/madencilik.1364137 . Pialy P, Nkoumbou C, Villiéras F, Razafitianamaharavo A, Barres O, Pelletier M, Ollivier G, Bihannic I, Njopwouo D, Yvon J, Bonnet J-P. Characterization for industrial applications of clays from Lembo deposit, Mount Bana (Cameroon). Clay Minerals v. 2008;43(3):415–35. https://doi.org/10.1180/claymin.2008.043.3.07 . Schulze DG. An introduction to soil mineralogy. Soil Mineralogy with Environmental Applications. Madison, WI: SSSA; 2002. pp. 1–35. https://doi.org/10.2136/sssabookser7.c1 . Gasparini E, Tarantino SC, Ghigna P. (2002). Gibbsite-kaolinite waste from bauxite beneficiation to manufacture ceramic products. In: Proceedings of the 6th International Symposium on Environmental Issues and Waste Management in Energy and Mineral Production, Calgary, pp. 345–350. Kagonbe BP, Tsozue D, Nzeukou AN, Ngos III, S. Mineralogical, Geochemical and Physico-Chemical Characterization of Clay Raw Materials from Three Clay Deposits in Northern Cameroon. J Geoscience Environ Prot. 2021;9(6):86–99. https://doi.org/10.4236/gep.2021.96005 . Rajput RK. (2004). Engineering Materials. S. Chand and Company Ltd, New Delhi, India. P. 473. ISBN: 8121919606, 9788121919609. Maged A, Abu El-Magd SA, Radwan AE, Kharbish S, Zamzam S. Evaluation insight into Abu Zenima clay deposits as a prospective raw material source for ceramics industry. Remote Sens Charact Sci Rep. 2023. 10.1038/s41598-022-26484-5 . Hartwell JM. The diverse uses of montmorillonite. Clay Miner. 1965;6(2). https://doi.org/10.1180/claymin.1965.006.2.05 . 111 – 118. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 27 Apr, 2026 Reviews received at journal 22 Apr, 2026 Reviewers agreed at journal 17 Apr, 2026 Reviewers agreed at journal 12 Apr, 2026 Reviewers agreed at journal 09 Apr, 2026 Reviewers invited by journal 09 Apr, 2026 Editor invited by journal 02 Apr, 2026 Editor assigned by journal 01 Apr, 2026 Submission checks completed at journal 27 Mar, 2026 First submitted to journal 27 Mar, 2026 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. 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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-9147332","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":621763574,"identity":"3dc67933-c887-4167-8a84-3d124193e899","order_by":0,"name":"Enerst Tata¹","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA0UlEQVRIiWNgGAWjYHAD5gMMDAYHiFWdYMDAw8CWQLIWHgMgiwgt/NJnDz78+eOPvD37mW/SBQV35BnYTyfg1SLZl5dszJNgYNjDk7tNeobBM8MGntwNeLUYnOExkwY6jLGHAaiFx+AwY4MEL34t9md4zH/+SDCw7+F/8wykxZ6gFgMeHjMGoMMSeyRy2EBaEglqkTjDYyzNk2ac3HPjmbE1j8Gz5DZCfuHv4TH8+MNGzra9P/nhbZ4/d2z72c/i14IJ2EhUPwpGwSgYBaMACwAAAjo/dZyI2pQAAAAASUVORK5CYII=","orcid":"","institution":"National Higher Polytechnic Institute (NAHPI), The University of Bamenda","correspondingAuthor":true,"prefix":"","firstName":"Enerst","middleName":"","lastName":"Tata¹","suffix":""},{"id":621763575,"identity":"1517629b-bac0-4f09-bdbd-10ca83387073","order_by":1,"name":"Kevin Ijunghi Ateh","email":"","orcid":"","institution":"National Higher Polytechnic Institute (NAHPI), The University of Bamenda","correspondingAuthor":false,"prefix":"","firstName":"Kevin","middleName":"Ijunghi","lastName":"Ateh","suffix":""},{"id":621763576,"identity":"b2af1a1a-f3b8-46aa-9794-34da41b3288e","order_by":2,"name":"Cheo Emmanuel Suh","email":"","orcid":"","institution":"Unversity of Bamenda","correspondingAuthor":false,"prefix":"","firstName":"Cheo","middleName":"Emmanuel","lastName":"Suh","suffix":""},{"id":621763577,"identity":"cb0f4d93-dc18-44bb-b869-669ac85dc4a9","order_by":3,"name":"Elisha Mutum Shemang","email":"","orcid":"","institution":"Botswana International University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Elisha","middleName":"Mutum","lastName":"Shemang","suffix":""}],"badges":[],"createdAt":"2026-03-17 10:09:26","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9147332/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9147332/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107481370,"identity":"7b8efd3a-3d0f-441f-9100-9cea157c4f39","added_by":"auto","created_at":"2026-04-22 02:17:29","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":697750,"visible":true,"origin":"","legend":"\u003cp\u003eLocation map of the study area: (a) South West Region in Cameroon; (b) Meme Division in the South West Region; (c) Meme Division with Kumba 3 Sub-Division highlighted with the study area in a red rectangle; (d) The geology of Ediki and environs with clayey occurrences (not to scale) at the center\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-9147332/v1/baa795ce19f4f487b1e1b1da.png"},{"id":107125550,"identity":"add67bb5-e182-42e9-90bd-aa6992e9a4b1","added_by":"auto","created_at":"2026-04-17 05:45:58","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":300375,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of kaolinite-dominant phases identified at Ediki (NK1: K ± H ± F; NK2: K ± F ± Mt ± I; NK4: K ± H ± F ± Mt; NK6: K ± It ± Mt; NK7: K ± He ± He ± F and NK8: K ± It ± Mt ± F)\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-9147332/v1/149148391eeed90c9456abde.png"},{"id":107481135,"identity":"7aeef90a-4329-4ab4-ac21-0a9cddf478dc","added_by":"auto","created_at":"2026-04-22 02:16:00","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":190562,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of the dominant halloysite clay mineral identified (NK3: H + I + F ± Q; NK5: H + K ± Mt and NK11: H ± Mt ± He)\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-9147332/v1/8465f0c406db03a945bb5c59.png"},{"id":107125553,"identity":"02942723-5599-4824-aca5-bc1c70c50727","added_by":"auto","created_at":"2026-04-17 05:45:58","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":102499,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of illite (NK9: It ± H ± I ± F ± Mt) and gibbsite (NK10: G ± Q ± H ± Mt) clay phases identified at Ediki\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-9147332/v1/e97c4760320c8e5e4e1e74a3.png"},{"id":107125554,"identity":"bb71fe60-c6a8-41f1-9784-4190aa56d096","added_by":"auto","created_at":"2026-04-17 05:45:58","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":174918,"visible":true,"origin":"","legend":"\u003cp\u003eMorphological structures of (a) kaolinite, (b) halloysite, and (c) gibbsite adapted from Shulze (2005)\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-9147332/v1/e37cdaba98fdd952a52b63fc.png"},{"id":107125557,"identity":"0fa07fde-b0aa-4ec3-93b5-1c3b111887f3","added_by":"auto","created_at":"2026-04-17 05:45:59","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1171462,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of the kaolinite dominant types: flat, plate-like (NK1 and NK2); pseudohexagonal, tightly packed kaolinite plates and flakes (NK4); fine platy particles and wavy flakes of kaolinites (NK6); tightly packed, well- or ill-formed tiny kaolinites (NK7); and pseudo-vermiform loose lotus-like flakes or onion skin texture (NK8)\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-9147332/v1/9e87f742a1016aea527af9bc.png"},{"id":107125555,"identity":"3114d0ba-e649-4e5f-86a2-0eed06a925b7","added_by":"auto","created_at":"2026-04-17 05:45:59","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":424584,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of halloysite showing spongy hydroid shapes (NK3), loosely stacked pseudo-spheroidal shapes (NK5), and rodlike tubes (NK11)\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-9147332/v1/bba9db95c47e76df007d0652.png"},{"id":107481372,"identity":"ee809d7b-19f3-4866-b31f-2eca017d50c1","added_by":"auto","created_at":"2026-04-22 02:17:29","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":407097,"visible":true,"origin":"","legend":"\u003cp\u003eScallop SEM of illite (NK9) and stalactitic aggregates of gibbsite (NK10) samples\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-9147332/v1/b1c5cad50b2f64235256f9ae.png"},{"id":107486276,"identity":"93eadfb6-c7e6-44af-b736-37e7ce18f56f","added_by":"auto","created_at":"2026-04-22 02:37:58","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4157796,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9147332/v1/e5f067ce-56d2-4224-b787-4102e4641732.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"XRD, SEM Characterisation and Economic Potentials of Volcaniclastic-Derived Clays from Ediki, Mungo Formation, SW Cameroon","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eClay minerals are economically important as development minerals, especially in developing nations, by virtue of their wide applications in industry and pharmaceutics and have been mined in world-class deposits such as Cornwall and Cape York Peninsula in England and Australia, respectively [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. These minerals are hydrous aluminosilicates that have particle sizes less than 2 \u0026micro;m. They are mostly plate-like in shape and become plastic when wet but stone hard when dry. Their formation is usually through surface weathering, precipitation, low-temperature metamorphism, and diagenesis [2\u0026thinsp;\u0026minus;\u0026thinsp;4]. Their formation depends on climatic conditions and overall soil development [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], with rock composition also playing a crucial role [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Tropical conditions with high rainfall, warm temperatures, and high biological activity accelerate chemical weathering, which creates environments that typically produce clays like vermiculite, illite, kaolinite, halloysite, and montmorillonite, along with non-clay minerals such as gibbsite, hematite, and goethite.\u003c/p\u003e \u003cp\u003eCameroon's geographical and geological setting favours widespread clay deposit formation [7\u0026thinsp;\u0026minus;\u0026thinsp;9]. Numerous deposits have been reported in many areas in Cameroon, with extensive characterisation of their nature and geochemical properties (e.g., [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. These materials have been valorised primarily for ceramic production, including bricks, tiles, and fine porcelain [12\u0026thinsp;\u0026minus;\u0026thinsp;14]. Southwestern Cameroon hosts ubiquitous clay occurrences that remain poorly investigated regarding their mineralogical characterisation. Previous work in the study area includes studies of kaolin profiles in the Mungo Formation [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] and characterisation of basement-derived clays in south-central Cameroon [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. This study aims to document the mineral assemblage of the Ediki clayey occurrences, construe their genesis, and highlight potential industrial applications using X-ray diffractometry and scanning electron microscopy.\u003c/p\u003e"},{"header":"2. Study Site","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Geographical situation\u003c/h2\u003e \u003cp\u003eEdiki is a locality in Kumba 3 Sub-Division of the South West Region of Cameroon (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e(a-d\u003c/b\u003e). It is bordered to the north by Mabonji, to the south by Mbalangi, to the east by the Mungo River, and to the west by Pete. The climate is tropical, with distinct rainy (April-September) and dry (October-March) seasons. The mean temperature is 25\u0026deg;C, with rainfall ranging from 2085 to 9086 mm and peaking in June and July [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. This high rainfall reflects Ediki's position in a hyper-humid coastal belt. The area is drained by the north-south flowing Mungo River and its dendritic tributaries. The topography is gentle, averaging 111 meters above sea level.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Geological setting of the study area\u003c/h2\u003e \u003cp\u003eGeologically, Ediki forms part of the Cretaceous-Quaternary Douala sub-sedimentary basin, which is the northwestern extension of the west-central coastal province [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The local rocks belong to the Mungo Formation, which overlies the Mundeck Formation. The Mungo Formation comprises sandstone, shale, limestone, marl, silty clays, and siltstone. Clay occurrences are hosted within Upper Cretaceous (Turonian-Cenomanian) sandstones of this formation, which are overlain by recent pyroclastics and basaltic boulders. Within the study area, discontinuous shale outcrops appear along intermittent stream beds, while fossiliferous limestone occurs in central Ediki and along the Mungo riverbanks. Recent alluvium deposits towards the east, particularly along riverbanks, overlie isolated undifferentiated basaltic volcanic rocks. A hiatus separates these recent deposits from the underlying Mungo Formation transitional sequence of shale, limestone, and fine-grained sandstone characteristic of a low-energy coastal environment.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Methods","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Sampling and Sample Preparation\u003c/h2\u003e \u003cp\u003eEleven clay samples were collected judgmentally from outcrops along the main road and railway cuttings. The selection criteria included colour variation, texture, clay horizon thickness, and the absence of visible contamination. The samples were collected vertically at intervals determined by outcrop extent. The clay occurrences sampled were closely associated with decomposed pyroclastics that overlay the cretaceous sandstones of the Mungo Formation of the Douala sub basin. The samples were then wrapped in labelled bags and transported to the Geology Laboratory of the University of Buea. At the laboratory, the samples were air-dried and crushed using an agate mortar and pestle. The crushed material was sieved and the clay fraction obtained after treatment in distilled water with caustic soda added for effective particle separation to obtain the \u0026lt;\u0026thinsp;2 \u0026micro;m. Four hundred grams of each clay fraction were sent to the Department of Earth and Environmental Sciences at the Botswana International University of Science and Technology (BIUST) for XRD and SEM analyses.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.2. X-ray Diffractometry (XRD) Analysis\u003c/h2\u003e \u003cp\u003eNo pre-treatment was applied to preserve all mineral phases within this size fraction. All the samples were subjected to ethylene glycol treatment for proper clay characterisation. Major mineral composition was determined semi-quantitatively on bulk fractions at the University of Botswana, Gaborone, using a Philips PW1710 X-ray diffractometer. The instrument utilized monochromatic Cu Kα radiation and an automatic divergence slit at 40 kV and 35 nA. Randomly oriented powder samples were mounted in aluminium holders and scanned from 5\u0026deg; to 90\u0026deg; 2θ with a step size of 0.02\u0026deg;, a scan speed of 1.2\u0026deg;/min, and a 0.5 s count time. Minerals were identified via multiple peak matches using the MacDiff software and its integrated mineral database. Diffractograms were interpreted using X'PERTR Data Collector software.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Scanning Electron Microscopy (SEM) Analysis\u003c/h2\u003e \u003cp\u003eSEM imaging was performed using a Philips XL30 Environmental Scanning Electron Microscope equipped with an energy-dispersive spectrometer. The clay fraction of each sample was mounted on aluminium stubs with carbon-coated conductive glue, then viewed and photomicrographed. SEM was used solely to characterise particle morphology; no chemical analyses from EDS are reported here.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e4.1. XRD Analysis of Clay Mineral Fraction\u003c/h2\u003e\n \u003cp\u003eXRD analyses identified kaolinite, halloysite, illite, gibbsite, montmorillonite, quartz, feldspar, ilmenite, magnetite, and hematite as the various mineral phases (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Kaolinite is the dominant clay mineral in the area, occurring as the predominant phase in six samples (NK1, NK2, NK4, NK6, NK7, NK8). Magnetite and hematite occur as traces in most samples except NK1 and NK3. Halloysite is the major mineral in three samples (NK3, NK5, NK11), while illite and gibbsite (non-clay mineral) dominate samples NK9 and NK10, respectively. Ilmenite occurs as traces in samples NK2, NK3, and NK9. Quartz is an insignificant phase, occurring in trace amounts in only two samples (NK3, NK10). Montmorillonite is also insignificant, appearing only in trace amounts in NK1. Feldspar, a non-clay mineral, appears in trace amounts in four samples (NK1, NK2, NK3, NK4).\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMineral phases identified at the Ediki clayey occurrences by XRD analyses\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eSAMPLE GROUP\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eSAMPLE NUMBER / COORDINATES\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eCOMPOUND NAME/DESCRIPTION\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eCHEMICAL FORMULA\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\" morerows=\"27\" rowspan=\"28\"\u003e\n \u003cp\u003eKAOLINITE (Fig. \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\" morerows=\"3\" rowspan=\"4\"\u003e\n \u003cp\u003eNK1:\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e550901E \u0026nbsp;501049N\u003c/div\u003e\n \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003cbr\u003e\u003c/div\u003e\u0026nbsp;\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e\u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eMontmorillonite-22A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eNa\u003csub\u003e0.3\u003c/sub\u003e(Al, Mg)\u003csub\u003e2\u003c/sub\u003e Si\u003csub\u003e4\u003c/sub\u003eO\u003csub\u003e10\u003c/sub\u003e (OH)\u003csub\u003e2\u003c/sub\u003e\u0026middot;8H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eIron (III) oxide\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eHalloysite (residual surrounding kaolinite peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u0026middot;2SiO\u003csub\u003e2\u003c/sub\u003e\u0026middot;xH\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eKaolinite (major mineral with minimal halloysite and feldspar)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e(OH)\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c2\" morerows=\"4\" rowspan=\"5\"\u003e\n \u003cp\u003eNK2\u003c/p\u003e\n \u003cp\u003e550974E 501243N\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eMagnetite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e2.75\u003c/sub\u003eTi\u003csub\u003e0.2\u003c/sub\u003e5O\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eIlmenite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFeTiO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eMagnetite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eKaolinite (Prominent peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e(OH)\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eFeldspar (at 20 theta)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eK\u003csub\u003e0.47\u003c/sub\u003e Na\u003csub\u003e0.43\u003c/sub\u003e Ca\u003csub\u003e0.10\u003c/sub\u003e Al\u003csub\u003e1.1\u003c/sub\u003e Si\u003csub\u003e2.9\u003c/sub\u003e O\u003csub\u003e8\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c2\" morerows=\"4\" rowspan=\"5\"\u003e\n \u003cp\u003eNK4\u003c/p\u003e\n \u003cp\u003e551404E 501427N\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eMagnetite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e0.65\u003c/sub\u003eFe\u003csub\u003e1.81\u003c/sub\u003eMg\u003csub\u003e0.42\u003c/sub\u003eAl\u003csub\u003e0.1\u003c/sub\u003eTi\u003csub\u003e0.03\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eHalloysite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026middot;2\u003c/sub\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eFeldspar\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eKaolinite (two highest peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e(OH)\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eIron (III) oxide\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c2\" morerows=\"4\" rowspan=\"5\"\u003e\n \u003cp\u003eNK6\u003c/p\u003e\n \u003cp\u003e551587E 501820N\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eIron (III) oxide (noisy peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eMagnetite (Noisy peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eHematite (Noisy peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eIllite (small peaks in between)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e2K\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e0\u0026middot;3\u003c/sub\u003eMgO\u0026middot;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026middot;24\u003c/sub\u003eSiO\u003csub\u003e2\u0026middot;12\u003c/sub\u003e H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eKaolinite (three major peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e(OH)\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c2\" morerows=\"3\" rowspan=\"4\"\u003e\n \u003cp\u003eNK7\u003c/p\u003e\n \u003cp\u003e551587E 501820N\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eHematite (small noisy peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eMagnetite (Small noisy peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e2.946\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eKaolinite (3 major peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e(OH)\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eFeldspar (1st small peak)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c2\" morerows=\"4\" rowspan=\"5\"\u003e\n \u003cp\u003eNK8\u003c/p\u003e\n \u003cp\u003e551706E 501696N\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eMagnetite (Noisy peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e2.929\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eHalloysite (high peak at the end)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u0026middot;2SiO\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eFeldspar (Noisy peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e(K, Na)(Si\u003csub\u003e3\u003c/sub\u003eAl)O\u003csub\u003e8\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eIllite (peak at 53.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e2K\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e0\u0026middot;3\u003c/sub\u003eMgO\u0026middot;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026middot;24\u003c/sub\u003e SiO\u003csub\u003e2\u0026middot;12\u003c/sub\u003e H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eKaolinite (2 highest peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e(OH)\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\" morerows=\"11\" rowspan=\"12\"\u003e\n \u003cp\u003eHALLOYSITE (Fig. \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e\n \u003cp\u003eNK3\u003c/p\u003e\n \u003cp\u003e551456E 501180N\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eFeldspar and quartz (smaller peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e(K, Na)(Si\u003csub\u003e3\u003c/sub\u003eAl)O\u003csub\u003e8\u003c/sub\u003e, SiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eHalloysite (2 high peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u0026middot;2SiO\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eIllite (last peak)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e2K\u003csub\u003e2\u003c/sub\u003eO\u0026middot;3Mg\u0026middot;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u0026middot;24SiO\u003csub\u003e2\u003c/sub\u003e\u0026middot;12H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c2\" morerows=\"4\" rowspan=\"5\"\u003e\n \u003cp\u003eNK5\u003c/p\u003e\n \u003cp\u003e551315E 501815N\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eFeldspar\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e(K, Na)(Si\u003csub\u003e3\u003c/sub\u003eAl)O\u003csub\u003e8\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eHalloysite (Highest peak)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u0026middot;2SiO\u003csub\u003e2\u003c/sub\u003e\u0026middot;xH\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eKaolinite (peak to its right)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eSi\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e(OH)\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eMagnetite high\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e2.945\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eIron (III) oxide\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c2\" morerows=\"3\" rowspan=\"4\"\u003e\n \u003cp\u003eNK11\u003c/p\u003e\n \u003cp\u003e552289E 501140N\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eHematite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eMagnetite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eHalloysite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026middot;2\u003c/sub\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u0026middot;xH\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eIllite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e2K\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e0\u0026middot;3\u003c/sub\u003eMgO\u0026middot;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u0026middot;24SiO\u003csub\u003e2\u003c/sub\u003e\u0026middot;12H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\" morerows=\"4\" rowspan=\"5\"\u003e\n \u003cp\u003eILLITE (Fig. \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\" morerows=\"4\" rowspan=\"5\"\u003e\n \u003cp\u003eNK9\u003c/p\u003e\n \u003cp\u003e552403E 501630N\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eMagnetite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eHalloysite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u0026middot;2SiO\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eFeldspar\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e(K, Na)(Si\u003csub\u003e3\u003c/sub\u003eAl)O\u003csub\u003e8\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eIllite (Prominent peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eKAl\u003csub\u003e2\u003c/sub\u003e(Si\u003csub\u003e3\u003c/sub\u003eAlO\u003csub\u003e10\u003c/sub\u003e)(OH)\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eilmenite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFeTiO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\" morerows=\"4\" rowspan=\"5\"\u003e\n \u003cp\u003eGIBBSITE\u003c/p\u003e\n \u003cp\u003e(Fig. \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\" morerows=\"4\" rowspan=\"5\"\u003e\n \u003cp\u003eNK10\u003c/p\u003e\n \u003cp\u003e552036E 500491N\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eMagnetite (Noisy peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eFe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eIron-magnesium compounds (noisy peaks)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eMg\u003csub\u003e0.208\u003c/sub\u003eFe\u003csub\u003e0.955\u003c/sub\u003eTi\u003csub\u003e0.833\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eQuartz (peak just before gibbsite)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eGibbsite (Highest peak)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl(OH)\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eHalloysite (Next peaks in height)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e2SiO\u003csub\u003e2\u003c/sub\u003e\u0026middot;x H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003eThese mineral phases can be grouped into four dominant categories: kaolinite, halloysite, illite, and gibbsite. The kaolinite group shows several associations: NK1, NK4, and NK8 contain kaolinite with halloysite, montmorillonite, feldspar, and magnetite; NK2 and NK7 have kaolinite with feldspar, magnetite, and ilmenite; NK6 contains kaolinite with illite and magnetite. Kaolinite peak intensities range from approximately 80 to over 150 counts, with halloysite and feldspar peaks in these samples below 50 counts.\u003c/p\u003e\n \u003cp\u003eAs seen in Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the halloysite group includes NK3, NK5, and NK11 (Fig. \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), with halloysite peaks exceeding 150 counts. NK5 shows halloysite with kaolinite and magnetite; NK11 contains halloysite with illite, magnetite, and hematite; NK3 includes halloysite with feldspar, ilmenite, and quartz.\u003c/p\u003e\n \u003cp\u003eThe illite phase is represented by sample NK9, showing illite with halloysite, magnetite, and feldspar. The gibbsite phase is sample NK10, containing gibbsite with quartz, halloysite, and magnetite (Fig. \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Illite XRD counts exceed 80, while gibbsite counts exceed 150.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e4.2. Clay Structure and Morphology\u003c/h2\u003e\n \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n \u003ch2\u003e4.2.1. Kaolinite Structure and Morphology\u003c/h2\u003e\n \u003cp\u003eKaolinite has a 1:1 layer structure with Al\u0026sup3;⁺ in octahedral sites and Si⁴⁺ in tetrahedral sites (Fig. \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The electrically neutral layers are held together by hydrogen bonding between basal oxygens and adjacent hydroxyl groups. This structure in its form limits isomorphous substitution, resulting in a nearly fixed chemical formula of Al\u003csub\u003e₂\u003c/sub\u003eSi\u003csub\u003e₂\u003c/sub\u003eO\u003csub\u003e₅\u003c/sub\u003e(OH)\u003csub\u003e₄\u003c/sub\u003e.\u003c/p\u003e\n \u003cp\u003eKaolinite in these samples displays various morphologies (Fig. \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). NK1 and NK2 show flat, plate-like crystals, while NK4, NK6, and NK7 exhibit aggregated pseudohexagonal, stacked crystal flakes. NK6 and NK8 contain loose pseudo-vermiform flakes. Most kaolinite particles lack parallel orientation and show face-to-edge fluctuations (NK1, NK2, NK7). This platelet morphology contributes to the material\u0026apos;s plasticity, which is important for ceramic applications.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n \u003ch2\u003e4.2.2. Halloysite Structure and Morphology\u003c/h2\u003e\n \u003cp\u003eHalloysite has a layered structure like kaolinite but with water molecules separating the 1:1 layer (Fig. \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). This higher water content makes it less stable, allowing transformation to kaolinite over time. SEM images reveal distinct halloysite morphologies, which are varied in the Ediki area (Fig. \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). NK3 shows spongy hydroid shapes, NK5 exhibits loosely stacked pseudo-spheroidal platelets, and NK11 reveals rod-like or tubular structures. This tubular morphology is particularly interesting for nanotechnology applications such as nano containers.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\n \u003ch2\u003e4.2.3. Illite and Gibbsite Structure and Morphology\u003c/h2\u003e\n \u003cp\u003eThe illite sample (NK9) displays scalloped edges, loose platelets with irregular elongated spines, and a cornflake texture with tightly packed crystals. The gibbsite sample (NK10) shows a typical crystalline structure with stalactite-like aggregates (Fig. \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"5. Discussion","content":"\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e5.1. Genetic Significance of Ediki\u003c/h2\u003e \u003cp\u003eClays generally form through silicate mineral instability, particularly feldspars, occurring in supergene weathering crusts, soils, continental and marine deposits, volcanic deposits, geothermal fields, altered wallrock, and low-grade metamorphic rocks [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Their formation depends on climate-rock interactions, which directly influence clay properties. Clay deposits are classified as primary (formed in situ) or secondary (sedimentary origin). Ideal conditions for kaolinitic clay formation include high rainfall, warm temperatures, lush vegetation, low relief, and high groundwater tables [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Field observations at Ediki show gradational contacts between clay concentrations and the overlying laterite cover and the pyroclastics, with clays near presumed volcanic parent rocks and pyroclastics. This supports in-situ formation through decomposition of the dominant pyroclastic deposits rather than the allochthonous hypothesis. The XRD analysis confirms kaolinite, halloysite, illite, and gibbsite as main constituents, with montmorillonite, feldspar, and iron oxides as accessories like other deposits in the coastal regions of Cameroon [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The Ediki clays likely formed from weathering of Mount Cameroon volcanic and volcaniclastic rocks, including basalts and ankaramite. They differ from Cretaceous kaolins of the Douala Sub-Basin, which contain kaolinite, smectite, and illite as major phases [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe clays are of supergene origin due to the absence of hydrothermal indicator minerals like pyrite that would suggest limited hydrothermal influence in contrast to the hydrothermally influenced deposits like Balengou n[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The parent rocks that decomposed are the same as those of other clay deposits along the Cameroon Volcanic Line [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. However, Ediki clays differ from northern Cameroon's quartz-rich smectitic clays formed under Sudano-Sahelian conditions [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Traces of montmorillonite in the clay materials from Ediki indicate chemical decomposition of volcanic ash rich in plagioclase feldspar. Halloysite typically forms from ultramafic rocks, volcanic glass, and pumice, often alongside kaolinite [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Illite within the Ediki deposit is derived from kaolinite chemical alteration under deep burial conditions through loss of interlayer water. The iron oxides point to a volcanic protolith, like clays reported from Mount Bana [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eGibbsite and illite in the Ediki area are likely formed at different depths, with gibbsite at shallow levels and illite at greater depths. Gibbsite forms through prolonged tropical weathering of aluminium-bearing minerals like feldspars [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Its presence indicates advanced weathering where silicon has been removed from kaolinite or halloysite, typically occurring in ferrosols where intense weathering prevents neo-feldspar formation [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe Ediki clay assemblage shows both similarities and differences with other Cameroonian deposits. Unlike smectite-rich northern clays [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e], Ediki clays are dominated by kaolinite-halloysite with very minor smectite content. They share similarities with other volcaniclastic-derived clays along the CVL [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] but differ from hydrothermally influenced Balengou deposits [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. This mineralogical diversity across Cameroon reflects variations in parent rock composition and weathering conditions.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e5.2. Commercial Applicability of the Ediki Clay\u003c/h2\u003e \u003cp\u003eThe economic value of clay is infrequently determined by its bulk chemical composition alone; rather, it is a direct function of its mineralogical structure and physicochemical properties Kaolinites have a 1:1 layer structure that does not expand, making it physically stable and resistant to high temperatures. The Ediki clay assemblage, characterised by dominant kaolinite and halloysite with subsidiary illite, trace quartz and feldspar, and very low montmorillonite content, presents several industrial opportunities. The economic application of the Ediki clay will be enhanced through further use of chemical characterisation methods including XRF and geotechnical characterisation to determine the Atterberg\u0026rsquo;s limits, shear strength index, volume change potential, hydraulic conductivity, and the natural moisture content to definitively determine the economic value. The XRD and SEM results permits a preliminary economic assessment of the Ediki deposit and paves the way for further research and resource definition.\u003c/p\u003e \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e \u003ch2\u003e5.3.1. Suitability for Ceramics\u003c/h2\u003e \u003cp\u003eClays have extensive industrial applications, including building bricks, water filters, rubber, pharmaceuticals, and personal care products. Kaolinite-rich clays are the most abundant and widely used worldwide. Ediki's kaolinite is suitable for ceramic fabrication due to its strength, plasticity, and refractoriness. The specific mineral association at Ediki, mainly kaolinite, halloysite, illite, and gibbsite with trace quartz, is appropriate for ceramic applications. Kaolinite provides essential strength, plasticity, and refractoriness. Illite promotes vitrification, which densifies final products. Quartz prevents cracking, shrinking, and warping while providing a uniform shape during sintering at 850\u0026ndash;1050\u0026deg;C for fired bricks and tiles [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e], with small amounts also improving water absorption properties. The very low smectite (montmorillonite) content is advantageous for ceramic building materials, as high smectite content can cause excessive shrinkage and cracking.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section3\"\u003e \u003ch2\u003e5.3.2. Potential for Nanotechnology (Halloysite)\u003c/h2\u003e \u003cp\u003eBeyond traditional uses, clays are increasingly employed in advanced materials and composites, including engineered ceramics, lightweight aggregates, hybrid metallo-ceramic composites, geopolymers, adsorbents, and pharmaceutical carriers [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Halloysite, a kaolin-group mineral, is primarily used in ceramics, but its applications in other industries are expanding due to unique properties [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Its suitability for nanotechnology depends on purity and the properties of its nano-sized tubular structure. Naturally occurring halloysite holds promise in nanotechnology due to unique physicochemical properties derived from its tubular morphology. With low global reserves, natural halloysite offers an economical alternative to synthetic nanomaterials. The association of halloysite with kaolinite at Ediki enhances the economic prospects of these materials.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section3\"\u003e \u003ch2\u003e5.3.3. Other Potential Uses\u003c/h2\u003e \u003cp\u003eMontmorillonite, though present only in trace amounts in one sample, has diverse applications, including oil drilling muds, soil additives for water retention, petroleum refining catalysts [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], pharmaceuticals, animal feed, desiccants, cosmetics, paper, and food industries. However, its trace occurrence at Ediki suggests these applications would require blending with higher-grade material. Gibbsite, though not a clay mineral, influences soil management in the area. It contributes to soil aggregate stability, reducing erosion susceptibility, and strongly adsorbs phosphorus, which can limit plant availability. Gibbsite also promotes soil particle flocculation, influencing soil structure and water movement.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"6. Conclusions","content":"\u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe Ediki area contains sandstones, siltstone, basalts, and recent pyroclastics of the Mungo Formation, with shale and limestone along riverbanks. Field observations support in-situ clay formation through intense tropical weathering of pyroclastics and undifferentiated mafic to ultramafic rocks.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eXRD reveals Ediki clays are predominantly kaolinite, halloysite, and illite. Kaolinite dominates six samples (NK1, NK2, NK4, NK6, NK7, NK8), halloysite dominates three (NK3, NK5, NK11), illite dominates NK9, and gibbsite dominates NK10. Minor components include trace montmorillonite (NK1 only), ilmenite, magnetite, hematite, quartz, and feldspar.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe mineral assemblage indicates formation through intense tropical weathering of pyroclastics, basalts, and associated volcaniclastic rocks. The presence of gibbsite signifies advanced leaching under warm, humid conditions. The absence of hydrothermal indicator minerals suggests supergene weathering without significant hydrothermal influence.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eKaolinite and halloysite are valuable for ceramics and pottery. Very low smectite content benefits ceramic applications. Tubular halloysite suggests the potential for higher-value applications in nanotechnology, adsorbents, and advanced composites. The overall assemblage is suitable for traditional ceramic building materials.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eEthics approval and consent to participate\u003c/h2\u003e \u003cp\u003eNot applicable.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eNot applicable.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eCompeting interests\u003c/strong\u003e \u003cp\u003eThe authors declare no competing interests\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eEnerst Tata: conceptualization, methodology, data curation, and writing of original draft. Ateh K. Ijunghi: visualization, writing- review \u0026amp; editing, validation. Cheo E. Suh and Elisha M. Shemang: Review \u0026amp; editing, validation of manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003e \u003cem\u003eThis contribution received funding from the International Union of Geological Sciences (IUGS) under its \"Resourcing Future Generations\" programme, coordinated by Prof. C.E. Suh at the University of Buea, Cameroon. Partial funding was also received through the Research and Modernisation Allowance (RMA) scheme provided to university lecturers in Cameroon by the Head of State.\u003c/em\u003e \u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eHarvey CC, Murray HH. Industrial clays in the 21st century: a perspective of exploration, technology and utilisation. 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Clay Miner. 1965;6(2). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1180/claymin.1965.006.2.05\u003c/span\u003e\u003cspan address=\"10.1180/claymin.1965.006.2.05\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. 111\u0026thinsp;\u0026ndash;\u0026thinsp;118.\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":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-geoscience","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Geoscience](https://www.springer.com/journal/44288)","snPcode":"44288","submissionUrl":"https://submission.nature.com/new-submission/44288","title":"Discover Geoscience","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"XRD, SEM, Clay, Cretaceous, Ediki, Cameroon","lastPublishedDoi":"10.21203/rs.3.rs-9147332/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9147332/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Cretaceous Mungo Formation in Ediki, situated in southwestern Cameroon, is characterised by sandstone, siltstone, and carbonates, overlain by pyroclastics and undifferentiated mafic rocks. Clayey occurrences are ubiquitously sandwiched within the sandstones. To determine the clay mineral diversity and commercial applicability, eleven clay samples were obtained through scooping and analysed by XRD and SEM methods. XRD results show kaolinite (NK1, NK2, NK4, NK6, NK7, NK8), halloysite (NK3, NK5, NK11), and illite (NK9) as major clay phases, while montmorillonite, feldspar, and quartz are associated with the clay. Magnetite, hematite, and ilmenite occur as impurities. Gibbsite is recorded in one sample (NK10). SEM reveals that the kaolinites are flat, plate-like, and lotus-like; halloysite is spongy, rod-like, and pseudo-spheroidal, while illite is scallop-shaped. The gibbsite sample is stalactitic. The clays are derived from the decomposition of the pyroclastics, ash, and ultramafic and mafic rocks. The iron oxide impurities are from mafic rocks, while quartz is derived from sandstone and siltstone. The occurrence of gibbsite indicates deep weathering in a warm, humid climate. Kaolinite and illite have potential use in ceramics, paper, and as components in cosmetics and toothpaste; montmorillonite and halloysite, as drilling fluids, catalysts, and adsorbents for environmental remediation, drug delivery, and to create stronger nanocomposites.\u003c/p\u003e","manuscriptTitle":"XRD, SEM Characterisation and Economic Potentials of Volcaniclastic-Derived Clays from Ediki, Mungo Formation, SW Cameroon","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-17 05:45:51","doi":"10.21203/rs.3.rs-9147332/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-04-27T19:59:57+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-22T11:39:55+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"159174262711512737026335206821076854454","date":"2026-04-17T16:57:42+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"315692218312522685809541206360972358586","date":"2026-04-12T17:28:44+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"155938087803497229474679023939009958536","date":"2026-04-09T10:05:41+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-09T07:32:11+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-04-02T07:48:08+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-01T04:08:54+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-27T09:20:03+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Geoscience","date":"2026-03-27T09:08:04+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-geoscience","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Geoscience](https://www.springer.com/journal/44288)","snPcode":"44288","submissionUrl":"https://submission.nature.com/new-submission/44288","title":"Discover Geoscience","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"385415ad-e883-4f2c-86fe-f2b1b5d8c528","owner":[],"postedDate":"April 17th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-17T05:45:51+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-17 05:45:51","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9147332","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9147332","identity":"rs-9147332","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}