Analyzing Optical Properties of Natural Fluorite Crystals: A Comprehensive Investigation

Analyzing Optical Properties of Natural Fluorite Crystals: A Comprehensive Investigation | 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 Analyzing Optical Properties of Natural Fluorite Crystals: A Comprehensive Investigation Maryam Shakooei, Mohammad Mahdi Shahidi, Arezoo Abedi, Mona Mehrabani This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4143001/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Fluorite, a primary fluorine mineral, plays a crucial role in various chemical and manufacturing processes. In this study focuses on the structural and optical characteristics of four natural fluorite crystals from the Era mine and Komsheche deposit in Iran. Raman spectroscopy, X-ray diffraction (XRD) analysis, photoluminescence (PL) spectroscopy, and diffuse reflectance spectroscopy were used to investigate the samples. The Raman spectra exhibited a distinctive peak at approximately 322 cm⁻¹, corresponding to the CaF₂ lattice vibration. XRD patterns confirmed the cubic phase of CaF₂, and the preferred orientation of the (111) crystallographic plane was observed. The study revealed variations in full-width at half-maximum (FWHM) values among the samples, potentially indicating the presence of yttrium and enabling differentiation of Various fluorites from different regions. The results provide valuable insights into the structural and optical properties of fluorite crystals and contribute to the understanding of their formation and potential applications in various fields. Fluorite Raman XRD PL DRS Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Fluorine compounds play a crucial role in various chemical and manufacturing procedures. Fluorspar, also known as a trade name of fluorite, is the primary fluorine mineral that is extensively mined. Fluorite is utilized directly as a material for fluxing and as an additive in diverse manufacturing processes. It serves as the primary source of fluorine in the creation of hydrogen fluoride or hydrofluoric acid, which is utilized as the raw material for numerous organic and inorganic chemical compounds. Fluorine plays a vital role in numerous industries, serving as an essential element in steelmaking, aluminum production, glass manufacturing, gasoline refining, and the production of enamels, insulating foams, refrigerants, and uranium for nuclear power [1]. Fluorite exhibits a chemical composition consisting of 51.2% calcium (Ca) and 48.8% fluorine (F). In some instances, it may contain chlorine (Cl), particularly in yellow varieties, as an isomorphous impurity or bituminous substances with a distinctive odor. Other impurities that may be present include iron oxide (Fe2O3), rare earth elements, and, on rare occasions, uranium, additional fluorine, and helium [2]. Fluorite, also known as CaF 2 , commonly contains impurities of Y in its crystalline structure. The Ca 2+ ions are arranged in a cubic coordination with F - ions. The positioning of Ca 2+ ions is such that they are distributed at both the corners and face centers within a cubic unit cell. On the other hand, F – ions are located at the centers of the eight smaller cubes resulting from the division of the unit cell. Each Ca 2+ ion is connected to eight F – ions situated at the corners of a cube, forming a coordination arrangement. Specifically, the Ca 2+ ions envelop the F – ions at the corners, creating a tetrahedral configuration, as depicted in Fig. 1. The system itself is cubic, resulting in crystal formations that can take the shape of cubes, octahedrons, cubic octahedrons, and occasionally rhomb dodecahedrons. At times, the crystals can form visually appealing druses. Fluorite can be found in massive and veined forms, appearing as spherulites or rhythmically banded spherulite aggregates. The mineral is predominantly colorless or white, but can also exhibit shades of purple and green. Occasionally, polychromatic zonal crystals can be discovered. Fluorite possesses perfect cleavage parallel to the octahedron [111]. It has a glassy lustre, a hardness of 4, and a density of 3.18 gr/t. Notably, fluorite exhibits a purple or blue luminescence. Fluorite is commonly found in hydrothermal mineral deposits, often coexisting with sulfides like galena, sphalerite, and/or pyrite. Additionally, it forms associations with minerals such as calcite, dolomite, gypsum, barite, and quartz. In granites and pegmatites, fluorite emerges as a late-stage crystallization product. Geodes may also contain deposits of fluorite [3,4]. Fluorite is easily identified due to its chemical and physical properties that enhance its vivid color and fluorescence. In geological fields, fluorite plays an important role in the concentration and precipitation of rare metals. Consequently, it is often found in association with rich deposits of these valuable elements. In addition, fluorite tends to exhibit trace element compositions that reflect the formation fluid chemistry prevalent under diverse mineralization conditions. This feature suggests that fluorite compositions associated with specific deposit types have unique signatures. Consequently, fluorite has the potential to become a valuable tracer or geochemical indicator mineral [5]. Iran has a significant abundance of fluorite resources, with more than 30 known deposits and estimated reserves of more than 500,000 tons, with a base reserve of about 1 million tons. Currently, mining activities are concentrated in four key locations across different provinces. The largest reserves of fluorite in Iran are located in Mazandaran province with 83,000 tons, followed by Khorasan province with a significant reserve of 326,000 tons. Also, Isfahan province has reserves of 120,000 tons and Kurdistan province has 5,000 tons of fluorite reserves [6]. This paper considers four natural fluorite crystals from the Era mine and Komsheche deposit which are located in the Mazandaran and Isfahan regions, respectively. Mazandaran Fluorspar Mining District (MFMD) is located in the east of central Alborz mountains in northern Iran. Geographically, fluorite mineralization in the MFMD is classified into three main areas: 1. Swadkoh region including Pachi Miana, Shesh Rudbar, Baijan, Drasleh, and Ashjal mines. 2. Khatirkoh region, which includes Kammarpesht, Sarchalshak, Shurchal, Shoorakchal, and Kharch mines. 3. Kiasar region, Era, and Alikola mines. The fluorite deposits in the MFMD are classified as Mississippi Valley fluorite-rich (MVT) deposits, and their host rock is known as Middle Triassic dolomite. Mineralization in these deposits includes a variety of minerals such as fluorite, barite, galena, calcite, pyrite and, dolomite [7-14]. The Komsheche deposit is located in the Middle Triassic dolomite of Central Iran in the Isfahan region. The type of ore deposit is MVT and the most important mineralization consists of Barite, Fluorite, Galena, Calcite, and Quartz [15-16]. The samples have been subjected to a comprehensive study to determine a method to evaluate their structural and optical characteristics. In this work, we compare the information obtained by Raman, photoluminescence and reflectance spectroscopy, and XRD diffraction studies. 2. Experimental 2.1. Materials This research was carried out on fluorite from two different areas in Iran. Fig. 2 shows three fluorite samples related to the Alborz region, Era fluorite mine (E, EB, FB), and one fluorite sample related to the Central Iran region, Komshecheh deposit (G). These samples have been investigated by Raman, Photoluminescence, diffused reflectance spectroscopy, and XRD analysis 2.2. Methods The investigation of all samples was conducted using a Micro Raman Spectroscope (532i Avantes). For each sample, three measurements were performed at distinct points. The diffraction peak intensity of the fluorite samples was normalized using Origin 2018 software. The X-ray diffraction (XRD) analysis was carried out using the AW-XDM300 instrument. This instrument is equipped with a CuK α radiation source with a wavelength of 1.54184 Å. The XRD data were collected with a step size of 0.05° 2θ, and each step had a counting time of 1 second. The photoluminescence emission (PL) spectra were tested by Shimadzu RF-600 fluorescence spectrometer. Diffuse Reflectance Spectroscopy (DRS) was tested using a UV-3600 spectrophotometer produced by Shimadzu, Japan. DRS measurements were recorded from 300 to 1800 nm. 3. Results and discussion 3.1. Raman spectroscopy The Micro-Raman spectra of the samples, utilizing a 532 nm excitation, are presented in Fig. 3 . In this figure, a distinctive Raman peak is consistently observed for all samples from different areas, appearing at approximately 322 cm⁻¹ [ 17 ]. This observation aligns with the fluorite peak documented in the RRUFF database (ID: R050046). Studies by Tsuda et al. [ 18 ] elucidated that this Raman signal corresponds to the CaF 2 lattice vibration at 322 cm⁻¹. Russell [ 19 ] obtained Raman peak of fluorite at 322 cm − 1 . Additionally, Liu et al. [ 20 ] reported a Raman peak at 320 cm − 1 for white fluorite. Lewandowski et al. [ 21 ] observed Raman peak at 319.13 cm − 1 for calcium fluoride. This specific peak at around 320–322 cm⁻¹ is attributed to the T 2g Raman active vibrational mode of fluorite [ 17 ], [ 22 – 26 ]. It's worth noting that white fluorite typically exhibits a single Raman peak at around 320 cm⁻¹, while non-white fluorite may display additional peaks at different locations [ 19 ]. In all analyzed specimens, the Raman active T 2g vibration mode of CaF 2 was observed. The observed frequency shift and full-width at half-maximum (FWHM) broadening of this mode are indicative of defects and impurities within the CaF 2 lattice [ 27 ]. The FWHM values for the samples E, EB, FB, and G are distinct, measuring 18.29, 17.67, 19.19, and 19.06, respectively. This variation in FWHM values among the samples may be attributed to the presence of yttrium in the samples, as indicated in Table 1 . FWHM is a critical parameter that can be used to differentiate fluorites originating from different regions. 3.2. XRD analysis Figure 4 displays the X-ray diffraction (XRD) patterns for all investigated samples. The diffraction peaks observed in the patterns can be accurately identified as (111), (220), (311), (400), (331), and (422) of the cubic phase of CaF 2 , characterized by the Fm3m (225) space group [ 28 – 30 ]. These findings are in agreement with the standard values ​​determined for cubic CaF 2 (ICSD No. 00-035-0816). we utilized Origin 2015 software to normalize the diffraction peak intensity of the fluorite samples. XRD results of fluorites indicate that the preferred orientation (111) for E, EB, FB, and G samples was observed at 2θ = 28.26°. Similarly, Wang et al. [ 29 ] showed the (1 1 1) crystallographic plane as the preferred orientation of CaF 2 . To study the fluorites from different regions, various parameters including peak position, the crystallite size (D) and, FWHM were measured and are detailed in Table 1 . The crystallite size for all samples was calculated using the Debye-Scherrer formula [ 31 – 32 ]. D = \(\frac{k{\lambda }}{\beta cos\theta }\) where β is the FWHM, λ is the wavelength of the X-ray (1.5418 Å), K is the Scherrer constant (usually K = 0.9) dependent on the crystallite shape and θ is the Bragg angle at the center of the peak. Table 1 provides the results obtained from the analysis of the X-ray data for different samples. Notably, the FWHM of the preferred orientation peak for samples E, EB, FB, and G is recorded as 0.12, 0.12, 0.11, and 0.13, respectively Additionally, the crystallite size for different samples was calculated using the dominant (111) peak, resulting in sizes of 67.6, 66.1, 73.2, and 59.8 nm, respectively. Il’ves et al. [ 33 ] calculated the FWHM of the diffraction peak of initial and annealed CaF 2 samples and obtained values of 0.141, 0.22 and, 0.101 for them. The study conducted by Zahedifar et al. [ 34 ] reported the crystallite size of CaF 2 using the dominant (220) peak, and the calculated value was approximately 43 nm. Table 1 The structural parameters of the four fluorite samples. Sample Peak position (2θ) FWHM (°) Crystallite size (nm) Raman Shift (cm − 1 ) FWHM (cm − 1 ) Y (ppm) E 28.26 0.12 67.6 322 18.29 1.5 EB 28.26 0.12 66.1 322 17.67 0.6 FB 28.26 0.11 73.2 322 19.19 3.4 G 28.26 0.13 59.8 322 19.06 2 3.3. ICP analysis The Yttrium (Y) content in fluorites was determined through Inductively Coupled Plasma (ICP) analysis. According to Table 2 , the highest Yttrium concentration is observed in the FB sample, with a value of 3.4 ppm, while the lowest concentration is found in the EB sample, at 0.6 ppm. The amount of yttrium in the E sample is 1.5 ppm and in the G sample is 2 ppm (Table 2 ). The comparison of Yttrium (Y) element values in different fluorites with FWHM values in Raman analysis revealed a direct relationship between FWHM and increasing Y values. Specifically, sample FB, with the highest Y value of 3.4 ppm, exhibited the highest FWHM. Conversely, sample EB, with the lowest Y value of 0.6 ppm, demonstrated the lowest FWHM [ 27 ]. Table 2 The average Yttrium values of the samples. Sample E EB FB G Y(ppm) 1.5 0.6 3.4 2 3.4. Photoluminescence Spectroscopy The simultaneous determination of the emission wavelength (Em) range and excitation wavelength (Ex) range for the samples can be achieved by measuring the 3D spectrum within the ranges of 400 to 600 nm for emission and 330 to 390 nm for excitation, respectively. In the representation of the 3D spectrum, the y-axis corresponds to the Ex, while the x-axis represents the fluorescence wavelength (Em) (Fig. 5 ). The color red is indicative of areas with strong fluorescence, whereas blue represents weaker fluorescence areas [ 35 ]. The analysis based on Fig. 5 involved the reduction of 3D images of photoluminescence (PL) in the emission range of 400 to 440 nm for samples E, EB, FB, and G, respectively. To validate this observation, the emission values of the samples were specifically investigated at 420 nm for an excitation wavelength of 350 nm, as shown in Table 3 . The study of the PL spectra of fluorite at excitation wavelengths of 260 nm aimed to investigate the factors contributing to the variation in PL emission (Fig. 6 ). Under the excitation of 260 nm, the PL emission peaks of samples E, EB, FB, and G are observed at 364 and 510 nm. Consequently, the PL emission peak of fluorites from different areas under a short wave is mainly at 510 nm, and the intensity is weak [ 20 ]. The presence of the Yttrium (Y) element is considered one of the reasons why fluorite exhibits fluorescence [ 20 ], [ 36 – 40 ]. According to Table 2 , the concentrations of Y in samples E, EB, FB, and G are recorded as 1.5, 0.6, 3.4, and 2 ppm, respectively. The study conducted by Liu et al. [ 20 ] involved an investigation of the photoluminescence (PL) spectra of fluorite at excitation wavelengths of 365 and 254 nm. The primary objective was to understand the factors contributing to the variation in PL emission. The study conducted by Il’ves et al. [ 33 ] investigated the photoluminescence (PL) of CaF2 samples, revealing broad bands with maxima at a wavelength of approximately λ max ~ 684 nm. The observation that the amount of fluorescence in the Alborz region samples (E, EB, FB) appears to be higher than in the Central Iran region sample (G) suggests a potential distinguishing characteristic between fluorites from these different regions. Table 3 Photoluminescence value of the samples at excitation 350 nm, Em 420nm. Sample E EB FB G Count 15836 7505 4213 4000 3.5. Diffuse Reflectance Spectroscopy The principle of diffuse reflectance spectroscopy is to measure the absorption of electromagnetic radiation within the wavelength range of 300 nm to 1800 nm. This absorption is caused by the vibrations of the molecular bonds in minerals, which include rotation, bending, and stretching motions, as they interact with the incident electromagnetic radiation. Various parameters, such as structure, cation size, charge, and electronegativity, determine the shape and precise position of the characteristic absorption bands for each mineral. These absorption bands offer valuable insights into the mineral's specific structure and composition [ 41 ]. Based on Fig. 7 , it is observed that in the ultraviolet range (300–400 nm), the samples E, EB, G, and FB exhibit the highest reflection intensity in that order. In the visible range (400–800 nm), as the wavelength increases, the highest reflectance is observed in the samples EB, G, E, and FB in that order. Similarly, in the infrared range, the samples EB, G, E, and FB show the highest intensity of reflection, respectively. The fluorite mineral has a large bandgap, which is located in the high-ultraviolet region at around 10 eV [ 42 ]. As a result, the absorption edge of fluorite occurs at 100 nm, leading to a high reflectance in the near-UV region (200 nm). Consequently, it becomes difficult to determine the precise band gap value [ 43 ]. Aimacaña et al. [ 43 ] conducted Diffuse Reflectance UV-Vis spectroscopy on part-CaF 2 powder to analyze its optical characteristics. Ge et al. [ 17 ] examined the UV-visible spectra of three fluorite samples with different colors. 4. conclusions In this study, the structural and optical properties of four fluorite samples from the Alborz and Central Iran regions in Iran were investigated. The Raman investigations indicated that the samples exhibited the same Raman shift; however, the presence of the Yttrium element resulted in different FWHM values.The XRD analysis revealed distinct crystal properties (crystallite size) for the fluorites from these two regions. Furthermore, 3D images of photoluminescence in the emission range of 400 to 440 nm displayed varying and decreasing emission values for the samples. The optical properties, as determined by reflectance measurements, showed that the reflection intensity of the samples differed and changed in the ultraviolet, visible, and infrared ranges. Declarations Author Contribution Maryam Shakooei: wrote the main manuscript text.Mohammad Mahdi Sahidi: ConceptualistArezoo Abedi : SupervisorMona Mehrabani: Prepared figures References Hayes TS, Miller MM, Orris GJ, Piatak NM (2017) Fluorine, Chapter G of Critical Mineral Resources of the United States—Economic and Environmental Geology and Prospects for Future Supply Betekhtin (1966) A course of mineralogy Milovsky AV, Kononov OV (1985) Mineralogy, Mir publishers Moscow Klein C, Philpotts AR (2013) Earth Materials: Introduction to mineralogy and petrology Makin S (2013) Developing fluorite as a geochemical pathfinder mineral using globally reported REE- Y contents. B.Sc. 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Philpotts, 2013).\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4143001/v1/e2ced9705995e4e46c862bf0.png"},{"id":53419486,"identity":"9e59c835-7855-4979-bd68-b55d5f780a20","added_by":"auto","created_at":"2024-03-25 18:12:14","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1164439,"visible":true,"origin":"","legend":"\u003cp\u003ePhotos of E, EB, FB and G samples.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4143001/v1/55a2a28126200287abd31c32.png"},{"id":53419488,"identity":"14b8341c-4041-4678-ba3c-f255d5b36165","added_by":"auto","created_at":"2024-03-25 18:12:15","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":110281,"visible":true,"origin":"","legend":"\u003cp\u003eRaman spectra of fluorites from Alborz (E, EB, FB) and Central Iran (G) regions in Iran.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4143001/v1/b7ac9a7611e54dfdf3361521.png"},{"id":53419487,"identity":"53cc7a9a-6b7a-4d9b-bd51-23e669478927","added_by":"auto","created_at":"2024-03-25 18:12:15","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":57017,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of four fluorites from different regions\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-4143001/v1/108084e4ccd5d53ab3acee58.png"},{"id":53419448,"identity":"229f4a44-f09b-43f3-aacb-77092d057f28","added_by":"auto","created_at":"2024-03-25 18:12:13","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":471610,"visible":true,"origin":"","legend":"\u003cp\u003e3D florescence Spectrum mode of the four fluorite samples.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-4143001/v1/44810e90306c8c00152e2547.png"},{"id":53419442,"identity":"c8c37a01-66da-413f-8ad0-ea6b96747cd5","added_by":"auto","created_at":"2024-03-25 18:12:13","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":109076,"visible":true,"origin":"","legend":"\u003cp\u003eEmission spectrum of samples at λ\u003csub\u003eEX\u003c/sub\u003e= 260 nm\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-4143001/v1/3167ac5d9c9882500baf6dec.png"},{"id":53419443,"identity":"9db54e58-7ddc-4c81-97f6-81f02fc05760","added_by":"auto","created_at":"2024-03-25 18:12:13","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":83298,"visible":true,"origin":"","legend":"\u003cp\u003eDiffuse reflectance spectrum of the four fluorite samples.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-4143001/v1/a17659197e0728d30306b746.png"},{"id":59304975,"identity":"892f7069-2d6f-4285-90a6-71355d8954a5","added_by":"auto","created_at":"2024-06-29 03:46:54","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3224718,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4143001/v1/6207c499-d117-447d-96a8-72c59c1f74ca.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Analyzing Optical Properties of Natural Fluorite Crystals: A Comprehensive Investigation","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eFluorine compounds play a crucial role in various chemical and manufacturing procedures. Fluorspar, also known as a trade name of fluorite, is the primary fluorine mineral that is extensively mined. Fluorite is utilized directly as a material for fluxing and as an additive in diverse manufacturing processes. It serves as the primary source of fluorine in the creation of hydrogen fluoride or hydrofluoric acid, which is utilized as the raw material for numerous organic and inorganic chemical compounds. Fluorine plays a vital role in numerous industries, serving as an essential element in steelmaking, aluminum production, glass manufacturing, gasoline refining, and the production of enamels, insulating foams, refrigerants, and uranium for nuclear power [1].\u003c/p\u003e\n\u003cp\u003eFluorite exhibits a chemical composition consisting of 51.2% calcium (Ca) and 48.8% fluorine (F). In some instances, it may contain chlorine (Cl), particularly in yellow varieties, as an isomorphous impurity or bituminous substances with a distinctive odor. Other impurities that may be present include iron oxide (Fe2O3), rare earth elements, and, on rare occasions, uranium, additional fluorine, and helium [2]. Fluorite, also known as CaF\u003csub\u003e2\u003c/sub\u003e, commonly contains impurities of Y in its crystalline structure. The Ca\u003csup\u003e2+\u003c/sup\u003e ions are arranged in a cubic coordination with F\u003csup\u003e-\u003c/sup\u003e ions. The positioning of Ca\u003csup\u003e2+\u003c/sup\u003e ions is such that they are distributed at both the corners and face centers within a cubic unit cell. On the other hand, F\u003csup\u003e\u0026ndash;\u003c/sup\u003e ions are located at the centers of the eight smaller cubes resulting from the division of the unit cell. Each Ca\u003csup\u003e2+\u003c/sup\u003e ion is connected to eight F\u003csup\u003e\u0026ndash;\u003c/sup\u003e ions situated at the corners of a cube, forming a coordination arrangement. Specifically, the Ca\u003csup\u003e2+\u003c/sup\u003e ions envelop the F\u003csup\u003e\u0026ndash;\u003c/sup\u003e ions at the corners, creating a tetrahedral configuration, as depicted in Fig. 1. The system itself is cubic, resulting in crystal formations that can take the shape of cubes, octahedrons, cubic octahedrons, and occasionally rhomb dodecahedrons. At times, the crystals can form visually appealing druses. Fluorite can be found in massive and veined forms, appearing as spherulites or rhythmically banded spherulite aggregates. The mineral is predominantly colorless or white, but can also exhibit shades of purple and green. Occasionally, polychromatic zonal crystals can be discovered. Fluorite possesses perfect cleavage parallel to the octahedron [111]. It has a glassy lustre, a hardness of 4, and a density of 3.18 gr/t. Notably, fluorite exhibits a purple or blue luminescence. Fluorite is commonly found in hydrothermal mineral deposits, often coexisting with sulfides like galena, sphalerite, and/or pyrite. Additionally, it forms associations with minerals such as calcite, dolomite, gypsum, barite, and quartz. In granites and pegmatites, fluorite emerges as a late-stage crystallization product. Geodes may also contain deposits of fluorite [3,4].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFluorite is easily identified due to its chemical and physical properties that enhance its vivid color and fluorescence. In geological fields, fluorite plays an important role in the concentration and precipitation of rare metals. Consequently, it is often found in association with rich deposits of these valuable elements. In addition, fluorite tends to exhibit trace element compositions that reflect the formation fluid chemistry prevalent under diverse mineralization conditions. This feature suggests that fluorite compositions associated with specific deposit types have unique signatures. Consequently, fluorite has the potential to become a valuable tracer or geochemical indicator mineral [5].\u003c/p\u003e\n\u003cp\u003eIran has a significant abundance of fluorite resources, with more than 30 known deposits and estimated reserves of more than 500,000 tons, with a base reserve of about 1 million tons. Currently, mining activities are concentrated in four key locations across different provinces. The largest reserves of fluorite in Iran are located in Mazandaran province with 83,000 tons, followed by Khorasan province with a significant reserve of 326,000 tons. Also, Isfahan province has reserves of 120,000 tons and Kurdistan province has 5,000 tons of fluorite reserves [6].\u003c/p\u003e\n\u003cp\u003eThis paper considers four natural fluorite crystals from the Era mine and Komsheche deposit\u0026nbsp;which are located in the\u0026nbsp;Mazandaran\u0026nbsp;and\u0026nbsp;Isfahan\u0026nbsp;regions, respectively.\u0026nbsp;Mazandaran Fluorspar Mining District (MFMD) is located in the east of central Alborz mountains in northern Iran. Geographically, fluorite mineralization in the MFMD is classified into three main areas:\u003c/p\u003e\n\u003cp\u003e1. Swadkoh region including Pachi Miana, Shesh Rudbar, Baijan, Drasleh, and Ashjal mines.\u003c/p\u003e\n\u003cp\u003e2. Khatirkoh region, which includes Kammarpesht, Sarchalshak, Shurchal,\u0026nbsp;Shoorakchal, and Kharch mines.\u003c/p\u003e\n\u003cp\u003e3. Kiasar region, Era, and Alikola mines.\u003c/p\u003e\n\u003cp\u003eThe fluorite deposits in the MFMD are classified as Mississippi Valley fluorite-rich (MVT) deposits, and their host rock is known as Middle Triassic dolomite. Mineralization in these deposits includes a variety of minerals such as fluorite, barite, galena, calcite, pyrite and, dolomite [7-14].\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;The Komsheche deposit is located in the Middle Triassic dolomite of Central Iran\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e in the Isfahan region. The type of ore deposit is MVT and the most important mineralization consists of Barite, Fluorite, Galena, Calcite, and Quartz [15-16].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe samples have been subjected to a comprehensive study to determine a method to evaluate their structural and optical characteristics. In this work, we compare the information obtained by Raman, photoluminescence and reflectance spectroscopy, and XRD diffraction studies.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cp\u003e\u003cstrong\u003e2.1. Materials\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was carried out on fluorite from two different\u0026nbsp;areas\u0026nbsp;in Iran. Fig. 2 shows three fluorite samples related to the Alborz region, Era fluorite mine (E, EB, FB), and one fluorite sample related to the\u0026nbsp;Central Iran\u0026nbsp;region, Komshecheh deposit (G). These samples have been investigated by Raman, Photoluminescence, diffused reflectance spectroscopy, and XRD analysis\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.2.\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe investigation of all samples was conducted using a Micro Raman Spectroscope (532i Avantes). For each sample, three measurements were performed at distinct points. The diffraction peak intensity of the fluorite samples was normalized using Origin 2018 software.\u003c/p\u003e\n\u003cp\u003eThe X-ray diffraction (XRD) analysis was carried out using the AW-XDM300 instrument. This instrument is equipped with a CuK\u003csub\u003e\u0026alpha;\u003c/sub\u003e radiation source with a wavelength of 1.54184 \u0026Aring;. The XRD data were collected with a step size of 0.05\u0026deg; 2\u0026theta;, and each step had a counting time of 1 second.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe photoluminescence emission (PL) spectra were tested by Shimadzu RF-600 fluorescence spectrometer.\u003c/p\u003e\n\u003cp\u003eDiffuse Reflectance Spectroscopy (DRS) was tested using a UV-3600 spectrophotometer produced by Shimadzu, Japan. DRS measurements were recorded from 300 to 1800 nm.\u003c/p\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Raman spectroscopy\u003c/h2\u003e \u003cp\u003eThe Micro-Raman spectra of the samples, utilizing a 532 nm excitation, are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. In this figure, a distinctive Raman peak is consistently observed for all samples from different areas, appearing at approximately 322 cm⁻\u0026sup1; [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. This observation aligns with the fluorite peak documented in the RRUFF database (ID: R050046). Studies by Tsuda et al. [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] elucidated that this Raman signal corresponds to the CaF\u003csub\u003e2\u003c/sub\u003e lattice vibration at 322 cm⁻\u0026sup1;. Russell [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] obtained Raman peak of fluorite at 322 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Additionally, Liu et al. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] reported a Raman peak at 320 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for white fluorite. Lewandowski et al. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] observed Raman peak at 319.13 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for calcium fluoride. This specific peak at around 320\u0026ndash;322 cm⁻\u0026sup1; is attributed to the T\u003csub\u003e2g\u003c/sub\u003e Raman active vibrational mode of fluorite [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], [\u003cspan additionalcitationids=\"CR23 CR24 CR25\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. It's worth noting that white fluorite typically exhibits a single Raman peak at around 320 cm⁻\u0026sup1;, while non-white fluorite may display additional peaks at different locations [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. In all analyzed specimens, the Raman active T\u003csub\u003e2g\u003c/sub\u003e vibration mode of CaF\u003csub\u003e2\u003c/sub\u003e was observed. The observed frequency shift and full-width at half-maximum (FWHM) broadening of this mode are indicative of defects and impurities within the CaF\u003csub\u003e2\u003c/sub\u003e lattice [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe FWHM values for the samples E, EB, FB, and G are distinct, measuring 18.29, 17.67, 19.19, and 19.06, respectively. This variation in FWHM values among the samples may be attributed to the presence of yttrium in the samples, as indicated in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. FWHM is a critical parameter that can be used to differentiate fluorites originating from different regions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.2. XRD analysis\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e displays the X-ray diffraction (XRD) patterns for all investigated samples. The diffraction peaks observed in the patterns can be accurately identified as (111), (220), (311), (400), (331), and (422) of the cubic phase of CaF\u003csub\u003e2\u003c/sub\u003e, characterized by the Fm3m (225) space group [\u003cspan additionalcitationids=\"CR29\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. These findings are in agreement with the standard values ​​determined for cubic CaF\u003csub\u003e2\u003c/sub\u003e (ICSD No. 00-035-0816). we utilized Origin 2015 software to normalize the diffraction peak intensity of the fluorite samples.\u003c/p\u003e \u003cp\u003eXRD results of fluorites indicate that the preferred orientation (111) for E, EB, FB, and G samples was observed at 2θ\u0026thinsp;=\u0026thinsp;28.26\u0026deg;.\u003c/p\u003e \u003cp\u003eSimilarly, Wang et al. [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] showed the (1 1 1) crystallographic plane as the preferred orientation of CaF\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo study the fluorites from different regions, various parameters including peak position, the crystallite size (D) and, FWHM were measured and are detailed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The crystallite size for all samples was calculated using the Debye-Scherrer formula [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003cem\u003eD\u003c/em\u003e =\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\frac{k{\\lambda }}{\\beta cos\\theta }\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003cp\u003ewhere β is the FWHM, λ is the wavelength of the X-ray (1.5418 \u0026Aring;), K is the Scherrer constant (usually K\u0026thinsp;=\u0026thinsp;0.9) dependent on the crystallite shape and θ is the Bragg angle at the center of the peak.\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e provides the results obtained from the analysis of the X-ray data for different samples. Notably, the FWHM of the preferred orientation peak for samples E, EB, FB, and G is recorded as 0.12, 0.12, 0.11, and 0.13, respectively Additionally, the crystallite size for different samples was calculated using the dominant (111) peak, resulting in sizes of 67.6, 66.1, 73.2, and 59.8 nm, respectively.\u003c/p\u003e \u003cp\u003eIl\u0026rsquo;ves et al. [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e] calculated the FWHM of the diffraction peak of initial and annealed CaF\u003csub\u003e2\u003c/sub\u003e samples and obtained values of 0.141, 0.22 and, 0.101 for them.\u003c/p\u003e \u003cp\u003eThe study conducted by Zahedifar et al. [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] reported the crystallite size of CaF\u003csub\u003e2\u003c/sub\u003e using the dominant (220) peak, and the calculated value was approximately 43 nm.\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\u003eThe structural parameters of the four fluorite samples.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" 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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\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\u003ePeak position\u003c/p\u003e \u003cp\u003e(2θ)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFWHM\u003c/p\u003e \u003cp\u003e(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCrystallite size (nm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRaman Shift (cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eFWHM (cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eY\u003c/p\u003e \u003cp\u003e(ppm)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eE\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e28.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e67.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e322\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e18.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eEB\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e28.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e66.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e322\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e17.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFB\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e28.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e73.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e322\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e19.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eG\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e28.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e59.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e322\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e19.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.3. ICP analysis\u003c/h2\u003e \u003cp\u003eThe Yttrium (Y) content in fluorites was determined through Inductively Coupled Plasma (ICP) analysis. According to Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the highest Yttrium concentration is observed in the FB sample, with a value of 3.4 ppm, while the lowest concentration is found in the EB sample, at 0.6 ppm. The amount of yttrium in the E sample is 1.5 ppm and in the G sample is 2 ppm (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe comparison of Yttrium (Y) element values in different fluorites with FWHM values in Raman analysis revealed a direct relationship between FWHM and increasing Y values. Specifically, sample FB, with the highest Y value of 3.4 ppm, exhibited the highest FWHM. Conversely, sample EB, with the lowest Y value of 0.6 ppm, demonstrated the lowest FWHM [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe average Yttrium values of the samples.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\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\u003eE\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eG\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eY(ppm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.4. Photoluminescence Spectroscopy\u003c/h2\u003e \u003cp\u003eThe simultaneous determination of the emission wavelength (Em) range and excitation wavelength (Ex) range for the samples can be achieved by measuring the 3D spectrum within the ranges of 400 to 600 nm for emission and 330 to 390 nm for excitation, respectively. In the representation of the 3D spectrum, the y-axis corresponds to the Ex, while the x-axis represents the fluorescence wavelength (Em) (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The color red is indicative of areas with strong fluorescence, whereas blue represents weaker fluorescence areas [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe analysis based on Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e involved the reduction of 3D images of photoluminescence (PL) in the emission range of 400 to 440 nm for samples E, EB, FB, and G, respectively. To validate this observation, the emission values of the samples were specifically investigated at 420 nm for an excitation wavelength of 350 nm, as shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eThe study of the PL spectra of fluorite at excitation wavelengths of 260 nm aimed to investigate the factors contributing to the variation in PL emission (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Under the excitation of 260 nm, the PL emission peaks of samples E, EB, FB, and G are observed at 364 and 510 nm. Consequently, the PL emission peak of fluorites from different areas under a short wave is mainly at 510 nm, and the intensity is weak [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The presence of the Yttrium (Y) element is considered one of the reasons why fluorite exhibits fluorescence [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], [\u003cspan additionalcitationids=\"CR37 CR38 CR39\" citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. According to Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the concentrations of Y in samples E, EB, FB, and G are recorded as 1.5, 0.6, 3.4, and 2 ppm, respectively.\u003c/p\u003e \u003cp\u003eThe study conducted by Liu et al. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] involved an investigation of the photoluminescence (PL) spectra of fluorite at excitation wavelengths of 365 and 254 nm. The primary objective was to understand the factors contributing to the variation in PL emission.\u003c/p\u003e \u003cp\u003eThe study conducted by Il\u0026rsquo;ves et al. [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e] investigated the photoluminescence (PL) of CaF2 samples, revealing broad bands with maxima at a wavelength of approximately λ\u003csub\u003emax\u003c/sub\u003e\u0026thinsp;~\u0026thinsp;684 nm.\u003c/p\u003e \u003cp\u003eThe observation that the amount of fluorescence in the Alborz region samples (E, EB, FB) appears to be higher than in the Central Iran region sample (G) suggests a potential distinguishing characteristic between fluorites from these different regions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePhotoluminescence value of the samples at excitation 350 nm, Em 420nm.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\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\u003eE\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eG\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCount\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15836\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7505\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4213\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e\u003cb\u003e3.5. Diffuse Reflectance Spectroscopy\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eThe principle of diffuse reflectance spectroscopy is to measure the absorption of electromagnetic radiation within the wavelength range of 300 nm to 1800 nm. This absorption is caused by the vibrations of the molecular bonds in minerals, which include rotation, bending, and stretching motions, as they interact with the incident electromagnetic radiation. Various parameters, such as structure, cation size, charge, and electronegativity, determine the shape and precise position of the characteristic absorption bands for each mineral. These absorption bands offer valuable insights into the mineral's specific structure and composition [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eBased on Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, it is observed that in the ultraviolet range (300\u0026ndash;400 nm), the samples E, EB, G, and FB exhibit the highest reflection intensity in that order. In the visible range (400\u0026ndash;800 nm), as the wavelength increases, the highest reflectance is observed in the samples EB, G, E, and FB in that order. Similarly, in the infrared range, the samples EB, G, E, and FB show the highest intensity of reflection, respectively.\u003c/p\u003e \u003cp\u003eThe fluorite mineral has a large bandgap, which is located in the high-ultraviolet region at around 10 eV [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. As a result, the absorption edge of fluorite occurs at 100 nm, leading to a high reflectance in the near-UV region (200 nm). Consequently, it becomes difficult to determine the precise band gap value [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAimaca\u0026ntilde;a et al. [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e] conducted Diffuse Reflectance UV-Vis spectroscopy on part-CaF\u003csub\u003e2\u003c/sub\u003e powder to analyze its optical characteristics. Ge et al. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] examined the UV-visible spectra of three fluorite samples with different colors.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. conclusions","content":"\u003cp\u003eIn this study, the structural and optical properties of four fluorite samples from the Alborz and Central Iran regions in Iran were investigated. The Raman investigations indicated that the samples exhibited the same Raman shift; however, the presence of the Yttrium element resulted in different FWHM values.The XRD analysis revealed distinct crystal properties (crystallite size) for the fluorites from these two regions. Furthermore, 3D images of photoluminescence in the emission range of 400 to 440 nm displayed varying and decreasing emission values for the samples. The optical properties, as determined by reflectance measurements, showed that the reflection intensity of the samples differed and changed in the ultraviolet, visible, and infrared ranges.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eMaryam Shakooei: wrote the main manuscript text.Mohammad Mahdi Sahidi: ConceptualistArezoo Abedi : SupervisorMona Mehrabani: Prepared figures\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eHayes TS, Miller MM, Orris GJ, Piatak NM (2017) Fluorine, Chapter G of Critical Mineral Resources of the United States\u0026mdash;Economic and Environmental Geology and Prospects for Future Supply\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBetekhtin (1966) A course of mineralogy\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMilovsky AV, Kononov OV (1985) Mineralogy, Mir publishers Moscow\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKlein C, Philpotts AR (2013) Earth Materials: Introduction to mineralogy and petrology\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMakin S (2013) Developing fluorite as a geochemical pathfinder mineral using globally reported REE- Y contents. B.Sc. Stockton University\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGhorbani M The Economic Geology of Iran: Mineral Deposits and Natural Resources, 2013, Springer, Dordrecht, 1\u0026ndash;450\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShafiei Bafti B, Dunkl I, Madanipour S (2021) Geological Magazine\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZabihitabar S, Shafiei B, Mirnejad H (2017) J Geol 9:75\u0026ndash;92\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVahab-zadeh G, Khakzad A, Rasae I, Mousavi MR (2008) J Sci 18:99\u0026ndash;108\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNabiloo F, Shafiei Bafti B, Amini A (2017) J Econ Geol 9:483\u0026ndash;507\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlirezaei S (1985) An investigation in stratigraphy and genesis of F-Pb-Ba deposits in the Central Alborz. M.S. thesis. Tehran University, Iran (in Persian)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMehraban Z (2016) Geochemistary of REEs in the fluorite (\u0026plusmn;\u0026thinsp;Pb, Ba) mine of Savadkuh region, Mazandaran province. M.S. thesis. 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In this study focuses on the structural and optical characteristics of four natural fluorite crystals from the Era mine and Komsheche deposit in Iran. Raman spectroscopy, X-ray diffraction (XRD) analysis, photoluminescence (PL) spectroscopy, and diffuse reflectance spectroscopy were used to investigate the samples. The Raman spectra exhibited a distinctive peak at approximately 322 cm⁻\u0026sup1;, corresponding to the CaF₂ lattice vibration. XRD patterns confirmed the cubic phase of CaF₂, and the preferred orientation of the (111) crystallographic plane was observed. The study revealed variations in full-width at half-maximum (FWHM) values among the samples, potentially indicating the presence of yttrium and enabling differentiation of Various fluorites from different regions. The results provide valuable insights into the structural and optical properties of fluorite crystals and contribute to the understanding of their formation and potential applications in various fields.\u003c/p\u003e","manuscriptTitle":"Analyzing Optical Properties of Natural Fluorite Crystals: A Comprehensive Investigation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-25 18:12:05","doi":"10.21203/rs.3.rs-4143001/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"240129cb-8335-40f2-b004-b2d2e53af1e1","owner":[],"postedDate":"March 25th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-06-29T03:38:41+00:00","versionOfRecord":[],"versionCreatedAt":"2024-03-25 18:12:05","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4143001","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4143001","identity":"rs-4143001","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}