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Minerals
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Gem Deposits: Mineralogical and Gemological Aspects, 2nd Edition
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Gem Deposits: Mineralogical and Gemological Aspects, 2nd Edition

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Deposits".

Deadline for manuscript submissions: 30 September 2024 | Viewed by 1514

Special Issue Editors

Prof. Dr. Andy H. Shen

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Guest Editor
Gemmological Institute, China University of Geosciences, Wuhan 430074, China
Interests: diamonds; colored stones; physical properties; geochemistry
Special Issues, Collections and Topics in MDPI journals
Dr. Chaowen Wang

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Guest Editor
Gemmological Institute, China University of Geosciences, Wuhan, China
Interests: mineralogy; clay minerals; gemmology; mineral deposits
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Bo Xu

E-Mail Website1 Website2
Guest Editor
School of Gemmology, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing, China
Interests: mineralogy; gemmology; ore deposits; geochemistry
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The Special Issue titled “Gem Deposits: Mineralogical and Gemological Aspects” has been very successful, and as we delved further into this particular subject, many more new aspects have shown up. Gemstones began being widely used in the manufacture of jewelry and art crafts as early as 7000 years ago. As the demand for gemstones increases, numerous new gem deposits have been exploited, and new gem species have infiltrated the market. However, the species of gemstones that share similar qualities can possess a wide range of values on the market as a result of their geographic origins. In the gem and jewelry trade, increased attention is being paid to the geographic origin of gemstones. Collections from a reliable gem deposit play a vital role in determining the geographic origins of certain gemstones. This Special Issue aims to present the latest, cutting-edge advances in gem deposits in relation to mineralogy, petrology, and gemology. The combined research into these related fields (for instance, geology, field gemology, geochemistry, geochronology, and spectroscopy) can provide important information concerning the formation of gemstones, enabling the comparison and geographic determination of gemstones worldwide.

This Special Issue invites submissions that include original scientific research relating to gem deposits from well-known and/or new localities worldwide. This Special Issue will focus on the following topics: (1) the geological background, occurrence, and genesis of gem deposits; (2) the mineralogical, gemological, geochemical, and spectroscopic characteristics of gemstones, with comparison between different deposits; (3) applying innovative new techniques (such as machine learning algorithms, etc.) to different gem deposits; (4) the applications of combined studies to trace the provenance of gemstones and highlight the methods of identifying gemstones.

Prof. Dr. Andy H. Shen
Dr. Chaowen Wang
Prof. Dr. Bo Xu
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • geochronology of gemstones
  • geological setting
  • genesis of gemstones
  • gemstone characterization
  • geographic origin

Related Special Issue

Published Papers (2 papers)

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Research

18 pages, 5124 KiB  
Article
Nephrite from Xinjiang Qiemo Margou Deposit: Gemological and Geochemical Insights
by Ting Fang, Yuan Chang and Mingxing Yang
Minerals 2024, 14(5), 458; https://0-doi-org.brum.beds.ac.uk/10.3390/min14050458 - 26 Apr 2024
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Abstract
The nephrite belt in the Altun Mountain–Western Kunlun Mountain region, which extends about 1300 km in Xinjiang, NW China, is the largest nephrite deposit in the world. The Qiemo region in the Altun Mountains is a crucial nephrite-producing area in China, with demonstrated [...] Read more.
The nephrite belt in the Altun Mountain–Western Kunlun Mountain region, which extends about 1300 km in Xinjiang, NW China, is the largest nephrite deposit in the world. The Qiemo region in the Altun Mountains is a crucial nephrite-producing area in China, with demonstrated substantial prospects for future exploration. While existing research has extensively investigated secondary nephrite deposits in the Karakash River and native black nephrite deposits in Guangxi Dahua, a comprehensive investigation of black nephrite from original deposits in Xinjiang is lacking. Margou black-toned nephrite was recently found in primary deposits in Qiemo County, Xinjiang; this makes in-depth research on the characteristics of this mine necessary. A number of technical analytical methods such as polarizing microscopy, Ultra-Deep Three-Dimensional Microscope, electron microprobe, back-scattered electron image analysis, X-ray fluorescence, and inductively coupled plasma mass spectrometry were employed for this research. An experimental test was conducted to elucidate the chemical and mineralogical composition, further clarifying the genetic types of the black and black cyan nephrite from the Margou deposit in Qiemo, Xinjiang. The results reveal that the nephrite is mainly composed of tremolite–actinolite, characterized by Mg/(Mg + Fe2+) ratios ranging from 0.86 to 1.0. Minor minerals include diopside, epidote, pargasite, apatite, zircon, pyrite, and magnetite. Bulk-rock rare earth element (REE) patterns exhibit distinctive features, such as negative Eu anomalies (δEu = 0.00–0.17), decreasing light REEs, a relatively flat distribution of heavy REEs, and low total REE concentrations (1.6–38.9 μg/g); furthermore, the Cr (6–21 μg/g) and Ni (2.5–4.5 μg/g) contents are remarkably low. The magmatic influence of granite appears to be a fundamental factor in the genesis of the magnesian skarn hosting Margou nephrite. The distinctive black and black cyan colors are attributed to heightened iron content, mainly associated with FeO (0.08~6.29 wt.%). Analyses of the chemical composition allow Margou nephrite to be classified as typical of magnesian skarn deposits. Full article
(This article belongs to the Special Issue Gem Deposits: Mineralogical and Gemological Aspects, 2nd Edition)
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14 pages, 15314 KiB  
Article
Changes in Blue Color of Sapphire Compared with Oxidation State Changes
by Ratthaphon Amphon, Chawalit Chankhantha, Chanisara Srimuang, Suchinda Vongsetskul, Saweat Intarasiri and Andy H. Shen
Minerals 2024, 14(4), 333; https://0-doi-org.brum.beds.ac.uk/10.3390/min14040333 - 25 Mar 2024
Viewed by 734
Abstract
Blue sapphire has long been treated with heat to modify its blue color and attain greater value. However, the process of modifying the blue color in sapphire remains not well understood. The color-changing mechanism has traditionally been explained using the Intervalence Charge Transfer [...] Read more.
Blue sapphire has long been treated with heat to modify its blue color and attain greater value. However, the process of modifying the blue color in sapphire remains not well understood. The color-changing mechanism has traditionally been explained using the Intervalence Charge Transfer (IVCT) (Fe2+-Ti4+ and/or Fe2+-Fe3+) theory, wherein the blue color can be diminished by heat treatment in an oxidizing environment which alters Fe2+ (FeO) to Fe3+ (Fe2O3) and decreases the occurrence of the IVCT process. However, recently, the band gap theory has been proposed, suggesting that iron (Fe) in sapphire is always in the Fe3+ state, the blue color is caused by Fe3+-Ti4+ pair and the heat treatment does not affect Fe oxidation state. Therefore, in this study, eight magmatic sapphires from four localities were investigated for changes in blue color via color analysis, changes in spectra using XANES, and changes in chemical composition using PIXE both before and after heat treatment. The color analysis reveals a slight reduction in saturation (fading of blue) and a noticeable lightening after heat treatment, which corresponds with the high content of solid inclusions or trapiche samples. XANES data analysis using the LCF technique indicated insignificant changes in Fe oxidation state from 2+ to 3+ after heat treatment across all samples. However, when comparing the XANES data with color parameter L*a*b*, it is noted that the percentage of Fe oxidation state changes does not show a positive relationship with changes in blue based on color parameter b* (blue–yellow); rather, it shows a positive relationship with parameter L* (lightness). Microscopic observations also reveal the dissolution of clouds or minute particles around planes of ilmenite needles. It could be suggested that the changes in Fe oxidation state may not be directly related to changes in blue color but could be linked to the partial dissolution of Fe-bearing inclusions. Full article
(This article belongs to the Special Issue Gem Deposits: Mineralogical and Gemological Aspects, 2nd Edition)
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