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Special Issue "New Trends in Gemstones and Jades at China University of Geosciences, Beijing"

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A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Mineralogical Crystallography and Biomineralization".

Deadline for manuscript submissions: 31 December 2023 | Viewed by 4883

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Special Issue Editors

Dr. Qingfeng Guo

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School of Gemology, China University of Geosciences, Beijing 100083, China
Interests: luminescence materials; crystal structure; gemology
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Ying Guo

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Guest Editor

School of Gemology, China University of Geosciences, Beijing 100083, China
Interests: luminescence materials; crystal structure; gemology; color origin and evaluation of gemstones
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Bo Xu

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State Key Laboratory of Geological Processes and Mineral Resources, School of Gemmology, China University of Geosciences, Beijing 100083, China
Interests: mineralogy; gemmology; ore deposits
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

From the tools and ornaments of the Stone Age to the fields of modern metallurgy, the chemical industry, medicine and aerospace, all reflect the close relationship between gems, minerals and human life. Gems is the general term used to refer to both natural gems and manufactured products. Gems and minerals can be divided into single-crystal gemstones, polycrystal gemstones, amorphous jades, organic materials and manufactured products, etc. Gems and minerals are rich in color, variety and quality, so it is of great significance to explore the gemological, color mechanism, spectral characteristics, chemical composition and crystal structure of gem minerals. This Special Issue aims to enrich the gemological and mineralogical library, and to update the comprehensive information on gems and minerals from around the world.

This Special Issue invites scholarly research on gemstones from scholars around the world. The topics of interest for the Special Issue mainly include but are not limited to the following: 1) The spectroscopic study of gems and minerals; 2) mineralogical characteristics of gems and minerals; 3) geographic and provenance determination of gems and minerals; 4) synthesis and enhancement of gems and minerals; 5) indicative significance of inclusions in gems and minerals.

Dr. Qingfeng Guo
Prof. Dr. Ying Guo
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. Crystals 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 2000 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

gemstones
spectroscopy
mineralogical characteristics

Published Papers (6 papers)

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Research

Open AccessArticle

Spectroscopic Characteristics and Coloring Mechanisms of Different Colored Spinels from Myanmar

Lei Zhang

Kui He

and

Qingfeng Guo

Crystals 2023, 13(4), 575; https://doi.org/10.3390/cryst13040575 - 28 Mar 2023

Viewed by 645

Abstract

Spinel is a common gemstone that has attracted the attention of gemologists worldwide because of its high refractive index, rich colors and brilliant hues. Myanmar is an important source of spinel. The present paper provides a systematic characterization of the gemological features of different color spinels from Myanmar, with a discussion and analysis of their color causes. The results show that complete octahedral crystal forms can be seen in Myanmar spinel, with the appearance of dissolution, growth motifs and cross-growth of crystals visible on the crystal surfaces. The XRF results show that the Myanmar red and orange spinel samples contain high levels of Cr, with the magenta sample having significant levels of Cr and the orange sample having more V. The blue and purple samples have high levels of Fe. The peaks of the infrared spectrum mainly appear around 841 cm⁻¹, 690 cm⁻¹ and 532 cm⁻¹. Raman spectra have peaks mainly around 310 cm⁻¹, 405 cm⁻¹, 663 cm⁻¹ and 764 cm⁻¹. According to the UV-Vis spectrum, the color of Myanmar red and orange spinels is mainly due to Cr³⁺ and V³⁺. When the Cr³⁺ content is higher than the V³⁺ content, the spinels show a red hue; when the V³⁺ content is higher than Cr³⁺, the spinels have an orange hue. Blue color is due to the charge transfer between Fe²⁺ and Fe³⁺. The research in this paper has enriched the gemological characteristics of Myanmar spinel and can provide a theoretical basis for its investigation, marketability, design and utilization. Full article

(This article belongs to the Special Issue New Trends in Gemstones and Jades at China University of Geosciences, Beijing)

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Open AccessArticle

Comparative Study on Gemmological Characteristics and Luminescence of Colorless and Yellow Scapolites

and

Crystals 2023, 13(3), 462; https://doi.org/10.3390/cryst13030462 - 08 Mar 2023

Viewed by 549

Abstract

The orange fluorescence of scapolite has been confirmed to be caused by (S₂)⁻, but the frequent blue fluorescence in gem-quality scapolite has not been well explained. An energy dispersive X-ray fluorescence spectrometer (XRF), electron probe microanalyzer (EPMA), X-ray powder diffractometer (XRD), Fourier transform infrared spectrometer (FTIR), Raman spectrometer, ultraviolet-visible spectrophotometer, fluorescence spectrometer, and conventional gemological test methods were used to study the gemological characteristics, chemical composition, coloration mechanism, spectral characteristics, and luminescence of colorless and yellow scapolite. The results show that both yellow and colorless scapolites are mizzonite and that they share the same gemological and spectroscopic characteristics. The results of XRD, FIRT, and Raman spectra show that the yellow scapolite has the same structure as the colorless scapolite. The yellow color of scapolite is caused by Fe³⁺ and when the Fe content is low it is colorless. Yellow scapolite has about three times the Fe content of colorless scapolite. Under the excitation of long-wave and short-wave ultraviolet light, scapolite forms a strong and wide excitation peak in the blue-violet region centered at approximately 410 nm, which is due to the 4f¹ → 5d¹ of Ce³⁺, resulting in blue fluorescence. Full article

(This article belongs to the Special Issue New Trends in Gemstones and Jades at China University of Geosciences, Beijing)

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Open AccessArticle

Investigation of Factors Affecting the Color of Serpentine Jade from Shandong, China

Shidie Deng

and

Ying Guo

Crystals 2023, 13(3), 431; https://doi.org/10.3390/cryst13030431 - 02 Mar 2023

Viewed by 521

Abstract

The color of serpentine jade is affected not only by the chemical composition, but also by some external factors. In this research, we quantitatively analyzed the color of serpentine jade and the influence of light sources, backgrounds, and thickness on its color. Thirty-six gem-quality serpentine jade samples from Tai’an, Shandong, China, were studied using eighteen Munsell neutral gray backgrounds, and three light sources (D65, F2, and A). It was found that the D65 light source appeared to be the most suitable for the display and sale of serpentine jade and the Munsell N9 background can make the color grading of serpentine jade more effective. Full article

(This article belongs to the Special Issue New Trends in Gemstones and Jades at China University of Geosciences, Beijing)

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Open AccessArticle

Comparative Study on Gemological and Mineralogical Characteristics and Coloration Mechanism of Four Color Types of Fluorite

and

Crystals 2023, 13(1), 75; https://doi.org/10.3390/cryst13010075 - 01 Jan 2023

Viewed by 1190

Abstract

Fluorite has been attracting the attention of gemstone mineralogists because of its rich color and excellent fluorescence properties. This paper studied fluorite with three color types (blue, green, and white) and five blue-purple fluorites with an alexandrite effect. Through the study of their structure, composition, and spectral characteristics, the gemological and mineralogical characteristics and coloration mechanisms of different color types of fluorites are compared and analyzed. The results show that the color of fluorite is caused by multiple color centers. Blue fluorite is associated with Y³⁺-F⁻ color center, while green fluorite is associated with a Y³⁺-Ce²⁺-F⁻ color center and Sm²⁺ color center, and white fluorite contains vacancy color center. The color of white fluorite is a mixture of yellow tones produced in visible light and blue fluorescence under UV light. Blue-purple color is caused by the colloid calcium color center and 2F⁻ color center, and its changing from blue-purple to red-purplish (alexandrite effect) are due to colloidal calcium nanoparticles caused by radioactive element Th. Full article

(This article belongs to the Special Issue New Trends in Gemstones and Jades at China University of Geosciences, Beijing)

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Open AccessArticle

Study on Gemological Characteristics and Inclusions of Yellow Topaz

Zixiong Song

Qingfeng Guo

and

Libing Liao

Crystals 2022, 12(12), 1746; https://doi.org/10.3390/cryst12121746 - 02 Dec 2022

Viewed by 739

Abstract

Topaz is a kind of mineral with variable composition and a common gemstone variety. Because of its wide distribution and rich colors, it has attracted the attention of scholars around the world. In this paper, the composition, spectral, and gemological characteristics of yellow topaz were systematically characterized, and the dark inclusions inside the samples were discussed and analyzed. The results show that the yellow topaz has a glassy luster, transparent, with a refractive index of 1.609–1.617 and a birefringence of 0.008. The topaz sample has columnar crystal shape and a typical rhomboid cross section. The infrared spectral characteristic absorption peaks of yellow topaz mainly appear near 3649, 3426, 950, 628, 550, and 457 cm⁻¹. The characteristic absorption peaks for Raman spectra are mainly at 937, 404, and 267 cm⁻¹. The UV-vis spectra of all samples only had strong absorption bands in the range of 200–300 nm. The results of XRF and EMPA showed that the contents of Al₂O₃ and SiO₂ in the samples were 52.79 (wt%) and 29.55 (wt%), respectively, and it was reasonable to speculate that the chromogenic element of the yellow color was iron. The inclusions in yellow topaz samples are mainly fluid inclusions, healing cracks, and albite. This paper has enriched the gemological characteristics of topaz and can provide theoretical data for the research and marketization of topaz. Full article

(This article belongs to the Special Issue New Trends in Gemstones and Jades at China University of Geosciences, Beijing)

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Open AccessArticle

Comparative Study of Mineralogical Characteristics of Natural and Synthetic Amethyst and Smoky Quartz

Kaichao Liu

and

Ying Guo

Crystals 2022, 12(12), 1735; https://doi.org/10.3390/cryst12121735 - 01 Dec 2022

Viewed by 764

Abstract

With the development of synthetic gem technology, a large number of synthetic rock crystals, such as natural and synthetic amethyst and natural and synthetic smoky quartz, have emerged in the market. Research on how to identify natural and synthetic amethyst, and natural and synthetic smoky quartz is of great significance. This paper systematically studied the mineralogical characteristics of natural and synthetic amethyst and natural and synthetic smoky quartz through X-ray powder diffraction, energy spectrum analysis, infrared spectroscopy, Raman spectroscopy, and ultraviolet visible light absorption spectroscopy. The results showed that the basic gemstone properties of natural and synthetic amethyst, natural and synthetic smoky quartz were very similar. The synthetic amethyst and smoky quartz could be seen bending cracks, with a small amount of bread crumb-like black inclusions under the polarizing microscope. Natural amethyst and smoky quartz had Raman characteristic peaks of about 697 cm⁻¹ and 1160 cm⁻¹, while synthetic amethyst and smoky quartz had no vibration peaks in these bands. Compared with the synthetic amethyst, the natural amethyst lacked the characteristic infrared absorption peak of 3500 cm⁻¹; compared with natural smoky quartz, synthetic smoky quartz lacked the 3484 cm⁻¹ infrared absorption peak. Full article

(This article belongs to the Special Issue New Trends in Gemstones and Jades at China University of Geosciences, Beijing)

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