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Spectroscopic Analysis for Harnessing the Quality and Potential of Gemstones for Small and Medium-Sized Enterprises (Smes)

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Spectroscopic Analysis for Harnessing the Quality and Potential of Gemstones for Small and Medium-Sized Enterprises (Smes) Hindawi Journal of Spectroscopy Volume 2021, Article ID 6629640, 12 pages https://doi.org/10.1155/2021/6629640 Research Article Spectroscopic Analysis for Harnessing the Quality and Potential of Gemstones for Small and Medium-Sized Enterprises (SMEs) Imtiaz Ahmad ,1 Suhail H. Serbaya ,2 Ali Rizwan ,2 and Malik Sajjad Mehmood 1 1Department of Basic Sciences, University of Engineering and Technology, Taxila, Pakistan 2Department of Industrial Engineering, King Abdulaziz University, Jeddah 21589, Saudi Arabia Correspondence should be addressed to Malik Sajjad Mehmood; [email protected] Received 9 December 2020; Revised 4 April 2021; Accepted 28 June 2021; Published 9 July 2021 Academic Editor: Daniel Cozzolino Copyright © 2021 Imtiaz Ahmad et al. +is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Introduction of modern technologies and methods and quality analysis for the gemstone industry are the main strategic initiatives of the Small and Medium Development Authority (SMEDA) of Pakistan. In this regard, four natural gemstones Quartz, Pyrope- Almandine Garnet, Black tourmaline, and Amethyst brought from Hunza valley Pakistan were analyzed by state-of-the-art spectroscopic techniques including EDX, UV-VIS, and FTIR spectroscopy. EDX revealed the traces of Fe, Mg, and Ca in Pyrope- Almandine garnet, Mg and Fe in Black tourmaline, Au and Ca in Amethyst. UV-VIS data revealed the values of Urbach energies 520, 210, 460, and 430 meV, and the values of direct bandgap energies 5.14, 6.12, 5.54, 5.74 eV, respectively. +e higher structural disorder due to the presence of Fe and other impurities in stones except Quartz was attributed to the higher values of Urbach energies and decrease in band gaps: FTIR data Fe-O and Si-O stretching vibration in Pyrope-Almandine garnet, Si-O bending vibrations and O-H stretching vibration in Quartz, Si-O-Si bending and stretching vibrations and C�O stretching vibrations in Black tourmaline, Ca-O stretching vibrations and Si-OH weak-vibrations in Amethyst. Photoluminescence results also showed useful information in investigating the properties of gemstones. 1. Introduction of gemstones has significant value for the commercial trade of natural gemstones. +erefore, a robust qualitative and Mineral deposits play a vital role in the economic devel- quantitative analytical technique is required for dis- opment of a country, and in this regard, Pakistan is well tinguishing synthetic and natural gemstones. In this regard, known for its abundance of natural resources and beauty. refractometers, polariscopes, hand spectroscope, and mi- Especially northern and northwestern areas are rich with croscopes were being used in gemstones identification in minerals incorporating precious and semiprecious gem- the past. Nowadays, most sophisticated techniques like stones. Of particular importance, these areas are blessed ultraviolet visible (UV-VIS) spectrometer, Raman spec- with huge reservoirs of ruby, sapphire, spinel, emerald, troscopy, infrared spectroscopy, electron dispersive X-ray Quartz, topaz, tourmaline, and aquamarine. +e afore- spectroscopy, and X-ray fluorescence (XRF) are used for mentioned types/classes of gemstones have great signifi- detail qualitative and quantitative analysis of natural cance due to their wide use in jewelry, as well as in gemstones in order to separate them from their artificial electronic, instrument, and scientific tools. It is, therefore, counterpart [1–4]. necessary to identify and distinguish natural gemstones +e color of the natural gemstones is the basic factor for from their synthetic counterparts to avoid the imitation of determining the quality and commercial significance, and natural ones. Most of the gemstones are colorless in nature there are multiple factors for the origin of these colors in gem and they are colored by some trace elements as impurities. minerals [2, 5–7]. Geologists have identified the following +ese trace elements can serve as fingerprints for the five mechanisms which are responsible for the color of identification and provenance of gemstones. Identification gemstones [8–10]. 2 Journal of Spectroscopy (i) Disperse metal ions causes the color in the gem- identification and classification on the basis of properties stones. Illumination of dispersed metal ions by a like color and inclusion, morphism (Iso and poly), anisot- light source absorbs certain wavelengths and can ropy (optical), crystallinity index, H2O contents, and pol- cause the electrons to jump to some temporary yphysicity, etc. +e associated functional groups were used higher state. Luminescence is emitted as energy for the estimation of all the abovementioned properties. from electrons and confers color to the gemstones. However, still, more in-depth analysis is required to have a +e recognition of the ion is not the only factor that precise qualitative and quantitative analysis of gemstones can affect the color of gemstones; other factors like from different localities. the valence state, nature of neighboring atoms, and In this paper, characterization of four natural gemstones ion coordination also take part in coloration in including Quartz (colorless), Pyrope-Almandine Garnet gemstones. (purplish-red), Black tourmaline, and Amethyst (light (ii) When the absorption occurs, then electrons jump purple) brought from Hunza valley (Gilgit Baltistan) is from one atom to another atom that causes the performed. All four precious ornaments are primarily coloration of the gemstones. characterized with EDX spectroscopy for investigating the trace elements. Subsequent to EDX, FTIR spectroscopy was (iii) Irradiation of gemstones can affect the metal ions performed to identify the major functional groups in each and change their oxidation state along with the sample. In addition, UV-VIS spectroscopy is performed to color center. figure out the Urbach energy, direct and indirect bandgap (iv) Absorption can be occurred due to the transition of energies of each stone. Actually, the main theme is to explore energy bands that can cause the color. the electronic transitions responsible for the color origi- (v) Phenomena like interference, scattering, diffraction, nation and to develop the correlation among the electronic and inclusion can change the color of gemstones. properties with the molecular ones. Furthermore, a Pho- toluminescence study was carried out to further investigate In order to have fully explored the nature of scientific the trace elements and meaningful information about the phenomena responsible for giving color to gemstones, identification of gemstones. various spectroscopic methodologies including UV-VIS, FTIR, XRD, XRF, EDX spectroscopy, are used [11–13]. In 2. Experimental this regard, Kassem et al. [14] have characterized the Quartz sample (milky color) belonging to a wadi of the eastern 2.1. Materials. Four natural gemstones which are investi- desert of Egypt, i.e., Araba, while using a number of tech- gated in this study are Quartz (colorless), Pyrope-Almandine niques including SEM, XRD, UV-VIS, FTIR, XRF, and Garnet (purplish-red), Black tourmaline, and Amethyst inductively coupled plasma-optical emission spectra (ICP- (light purple). +ese samples were brought from Hunza OES) and electron spin resonance (ESR) technique to assess valley (Gilgit Baltistan), Pakistan. +e information about the the radiation treatment effect on the color of Quartz. +e chemical composition of each stone is given below. FTIR spectra results revealed the increased absorption bands for [Al- OH/Na]+ and [Al-OH/Li]+ on irradiation. UV-VIS (i) Quartz is the most abundant mineral in the crust of spectra reveal an increase in bandgap properties on irra- Earth and is found in tetrahedron form, and its diation while ESR spectroscopy has shown a significant chemical composition is SiO2. increase in peak intensity. Although Kassem et al. [14] have (ii) Pyrope-Almandine Garnet is a mixed variety of used many techniques, unfortunately, the correlation among pyrope and almandine garnet, and its general for- the results of different experimental techniques is missing to mula is (Mg, Fe)3Al2(SiO4)3. have a solid conclusion. In another study, Branca et al. [15] (iii) Tourmaline constitute the supergroup minerals and utilized the SEM, XRD, Raman, and FTIR spectroscopy for a its general formula is XY3Z6 [T6O18][BO3]3V3W; In qualitative investigation of five types of emerald samples which X can be Na, K, Ca, Pb+2; Y can be Li, Mg, from different localities. +ey have used the Gaussian Fe2+, Mn2+, Cu2+, Al, V3+, Cr3+, Fe3+, Mn3+, Ti4+; Z deconvolution for the identification/quantification of OH can be Mg, Fe2+, Al, V3+, Cr3+, Fe3+; T can be Si, B, and Si-O contents while figuring out the hidden peaks in Al; B �B; V can be OH, O; W can be OH, F−,O2_. −1 −1 3400–3800 cm and 1000–1300 cm , respectively. In ad- Black tourmaline is a black color variety of tour- dition to peak deconvolution, they also used spectral dif- maline group, and its chemical formula is NaFe3[Al, ferentiation for establishing the proper correlation for alkali Fe]6[Si6O18][BO3]3[OH]3OH. contents within the beryl channels. However, a major (iv) Amethyst is the purple color variety of Quartz and limitation of this smart systemic approach is its narrow line its composition is the same as that of Quartz. +e of investigation as far as the regime of the research area is purple color of Amethyst is caused by the traces of
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