Editorial

3 pages, 178 KiB

Open AccessEditorial

Editorial for the Special Issue “Gem Characterisation”

by Stefanos Karampelas and Emmanuel Fritsch

Minerals 2024, 14(4), 350; https://doi.org/10.3390/min14040350 - 28 Mar 2024

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Gem characterisation is an ever-increasing challenge, especially with hard-to-detect treatments and new demands regarding origin determination [...] Full article

(This article belongs to the Special Issue Gem Characterisation)

Research

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17 pages, 6040 KiB

Open AccessArticle

Dehydration of Diaspore and Goethite during Low-Temperature Heating as Criterion to Separate Unheated from Heated Rubies and Sapphires

by Michael S. Krzemnicki, Pierre Lefèvre, Wei Zhou, Judith Braun and Georg Spiekermann

Minerals 2023, 13(12), 1557; https://doi.org/10.3390/min13121557 - 18 Dec 2023

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Abstract

Gem-quality rubies and sapphires are often commercially heat treated at about 800 °C or higher to enhance their color and clarity, and hence quality. For this study, selected corundum samples containing diaspore and goethite inclusions were heated step-by-step to a maximum of 1000 [...] Read more.

Gem-quality rubies and sapphires are often commercially heat treated at about 800 °C or higher to enhance their color and clarity, and hence quality. For this study, selected corundum samples containing diaspore and goethite inclusions were heated step-by-step to a maximum of 1000 °C with the aim of monitoring the dehydration and phase transformation of these oxyhydroxides to corundum and hematite during heating. Based on our experiments and in agreement with the literature, the dehydration of diaspore in corundum occurs between 525 and 550 °C, whereas goethite transforms to hematite between 300 and 325 °C. As both diaspore and goethite may be present as inclusions in rubies, sapphires, and other corundum varieties (e.g., pink sapphires, padparadscha), these dehydration reactions and phase transformations can be considered important criteria to separate unheated from heated stones, specifically in cases in which other methods (e.g., microscopy, FTIR) are unsuccessful. Full article

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17 pages, 6352 KiB

Open AccessArticle

Update on Emeralds from Kagem Mine, Kafubu Area, Zambia

by Ran Gao, Quanli Chen, Yan Li and Huizhen Huang

Minerals 2023, 13(10), 1260; https://doi.org/10.3390/min13101260 - 27 Sep 2023

Cited by 1 | Viewed by 1546

Abstract

Kagem emerald mine in Zambia is deemed to the largest open-pit emerald mine with extremely high economic value and market share in the world. To meet the market demand for tracing the origin of emeralds, 30 emeralds from the region were tested, and [...] Read more.

Kagem emerald mine in Zambia is deemed to the largest open-pit emerald mine with extremely high economic value and market share in the world. To meet the market demand for tracing the origin of emeralds, 30 emeralds from the region were tested, and some discoveries were made compared to previous studies. This study provides a full set of data through standard gemological properties, inclusions, color characteristics, advanced spectroscopic and chemical analyses, including Raman, micro micro-UV-Vis-NIR, FTIR, and LA-ICP-MS. The most common inclusions in Kagem emeralds are two-phase inclusions, which exhibit elongated, hexagonal, oval, irregular shapes or appear as negative crystals with incomplete hexagonal prism. These inclusions consist of H₂O or H₂O + CO₂ (liquid) and CO₂ + N₂ or CO₂ + N₂ + CH₄ (gas). Mineral inclusions typically include actinolite, graphite, magnetite, and dolomite. Black graphite encased in actinolite in Kagem emeralds is first reported. The FTIR spectrum of Kagem emeralds reveals that the absorption of type II H₂O is stronger than that of type I H₂O, indicating the presence of abundant alkali metals, which was confirmed through chemical analysis. Kagem emeralds contain high levels of Na (avg. 16,440 ppm), moderate-to-high Cs (avg. 567 ppm), as well as low-to-moderate levels of K (avg. 185 ppm) and Rb (avg. 14 ppm) concentrations. Full article

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24 pages, 9247 KiB

Open AccessArticle

Mineralogy of Agates with Amethyst from the Tevinskoye Deposit (Northern Kamchatka, Russia)

by Evgeniya N. Svetova, Galina A. Palyanova, Andrey A. Borovikov, Viktor F. Posokhov and Tatyana N. Moroz

Minerals 2023, 13(8), 1051; https://doi.org/10.3390/min13081051 - 09 Aug 2023

Cited by 1 | Viewed by 1439

Abstract

The Tevinskoye agate deposit is located in the North of the Kamchatka peninsula (Russia) and represented by agate-bearing Eocene basaltic and andesitic rocks of the Kinkilsk complex. Agate mineralization occurs in lavas and tuffs as amygdales, geodes, lenses and veins, which are the [...] Read more.

The Tevinskoye agate deposit is located in the North of the Kamchatka peninsula (Russia) and represented by agate-bearing Eocene basaltic and andesitic rocks of the Kinkilsk complex. Agate mineralization occurs in lavas and tuffs as amygdales, geodes, lenses and veins, which are the main sources of the resupply of coastal agate placers. The present study aimed to perform a comprehensive mineralogical, geochemical, and O-isotope investigation of amethyst-bearing agates, and to evaluate data concerning the origin of mineralization and the conditions for amethyst formation. Agates exhibit spectacular textures, with variation in the sequence of silica filling of amygdales and geodes. The mineral composition of the agates is mainly represented by micro- and macro-crystalline quartz, amethyst, length-fast and zebraic chalcedony, moganite, goethite, and clinoptilolite. Carbonate forms individual bands in the outer zones of some agates. The presence of small amounts of native copper, covellite, chalcopyrite and pyrite is a feature of these agates. Copper and iron mineralization are probably typomorphic features related to the host rock composition. The measured values of crystallite size (525–560 Å) and the high moganite content (up to 50%) of agate with amethyst are evidenced by the young age (~45 Ma) of agate-hosting rocks. Agate formation temperatures (21–229 °C) were calculated from the O-isotope composition of chalcedony (+19.6 to +25.5‰), quartz (+18.1 to +22.3‰), and amethyst (+18.2 to +21.5‰). The cold-water monophase fluid inclusions revealed in amethyst crystals suggest that the mineralizing fluids have low temperatures (<100 °C) and low salinity. Magnetite grains in host rock, together with goethite inclusions identified within the amethyst crystals, point to a change in redox conditions and the presence of iron in the agate-forming fluids, which entered the quartz lattice during crystallization and influenced the formation of the violet color. Full article

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14 pages, 6520 KiB

Open AccessArticle

Pink to Purple Sapphires from Ilakaka, Madagascar: Insights to Separate Unheated from Heated Samples

by Stefanos Karampelas, Ugo Hennebois, Jean-Yves Mevellec, Vincent Pardieu, Aurélien Delaunay and Emmanuel Fritsch

Minerals 2023, 13(5), 704; https://doi.org/10.3390/min13050704 - 22 May 2023

Cited by 3 | Viewed by 1536

Abstract

The present study is focused on the analysis of zircon inclusions found in pink to purple sapphires from Ilakaka (Madagascar) with an optical microscope, Fourier-transform infrared (FTIR), and micro-Raman spectroscopy in order to update previous knowledge and find insights to separate heated from [...] Read more.

The present study is focused on the analysis of zircon inclusions found in pink to purple sapphires from Ilakaka (Madagascar) with an optical microscope, Fourier-transform infrared (FTIR), and micro-Raman spectroscopy in order to update previous knowledge and find insights to separate heated from unheated samples. In total, 157 zircon inclusions in 15 unheated samples and 74 zircon inclusions in 6 heated samples are analysed using micro-Raman spectroscopy with standardised parameters. The full width at half maximum (FWHM) of the main Raman band due to anti-symmetric stretching vibration ν₃ of the SiO₄ tetrahedron in the zircon structure has been carefully measured. In the unheated samples, it ranges from 6.26 to 21.73 cm⁻¹ with an average of 10.74 cm⁻¹, a median of 10.04 cm⁻¹, and a standard deviation of 2.84 cm⁻¹. On the other hand, it is lower in the heated samples, ranging from 4.83 to 14.97 cm⁻¹ with an average of 7.23 cm⁻¹, median of 7.06 cm⁻¹, and standard deviation of 1.63 cm⁻¹. In our unheated samples, the FWHM was rarely below 7 cm⁻¹. In our heated samples, the FWHM was rarely above 12 cm⁻¹ but mostly below 8 cm⁻¹, with a variation restricted to less than 3 cm⁻¹ in the same sample. The present work will hopefully further contribute to more accurately identifying the low-temperature heat treatment of pink sapphires from Ilakaka, Madagascar. Full article

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15 pages, 3645 KiB

Open AccessArticle

Study of 405 nm Laser-Induced Time-Resolved Photoluminescence Spectroscopy on Spinel and Alexandrite

by Wenxing Xu, Tsung-Han Tsai and Aaron Palke

Minerals 2023, 13(3), 419; https://doi.org/10.3390/min13030419 - 16 Mar 2023

Cited by 1 | Viewed by 1513

Abstract

Research on photoluminescence spectroscopy on Cr-doped gem materials has demonstrated great success regarding the identification of gemstones in terms of building rapid test systems. In this study, 405 nm photoluminescence spectroscopy was used to measure the luminescence decay profiles of dozens of natural [...] Read more.

Research on photoluminescence spectroscopy on Cr-doped gem materials has demonstrated great success regarding the identification of gemstones in terms of building rapid test systems. In this study, 405 nm photoluminescence spectroscopy was used to measure the luminescence decay profiles of dozens of natural and lab-grown spinel (including heated spinel) and alexandrite. Spinel and alexandrite are both capable of producing photoluminescence with a long lifetime: spinel between 9 and 23 microseconds and alexandrite from 25 to 53 microseconds. The photoluminescence lifetime and exponential parameters of the half-life demonstrated notable differences in the ranges of decay times between natural, heated, and lab-grown versions of these materials. Full article

(This article belongs to the Special Issue Gem Characterisation)

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22 pages, 8996 KiB

Open AccessArticle

Purple-Violet Gem Spinel from Tanzania and Myanmar: Inclusion, Spectroscopy, Chemistry, and Color

by Jinlin Wu, Xueying Sun, Hong Ma, Peiying Ning, Na Tang, Ting Ding, Huihuang Li, Tianyang Zhang and Ying Ma

Minerals 2023, 13(2), 226; https://doi.org/10.3390/min13020226 - 04 Feb 2023

Cited by 2 | Viewed by 2383

Abstract

Purple-violet gem spinels from Tanzania and Myanmar have been investigated for their gemological, spectroscopic, chemical, and colorimetric characteristics. Samples TS and MS both had a purple hue with a pinkish or brownish secondary tone and medium–strong saturation. We identified a number of inclusions, [...] Read more.

Purple-violet gem spinels from Tanzania and Myanmar have been investigated for their gemological, spectroscopic, chemical, and colorimetric characteristics. Samples TS and MS both had a purple hue with a pinkish or brownish secondary tone and medium–strong saturation. We identified a number of inclusions, including dolomite, phlogopite, and forsterite in Tanzanian spinel and magnesite, apatite, baddeleyite, anhydrite, pyroxene, and graphite in Myanmar spinel. Tanzanian spinels have slightly lower FWHM (full width at half maximum) values of the 406 cm⁻¹ line in the Raman spectrum and the Cr³⁺ zero phonon line in the PL spectrum compared to samples from Myanmar. Fe, Mn, Cr, V, and Zn are proved as useful discriminators to distinguish these two geographic locations. UV-Vis-NIR spectra and CIE L*a*b* parameters are compared with trace element chemistry. Both samples are colored by Fe²⁺, with minor Fe³⁺, Cr³⁺, and V³⁺. Cr, V, and Fe are combined to influence the hue angle and lightless of purple spinels from Tanzania. However, due to the relatively stable content in Myanmar samples, Fe shows a minor effect on these two parameters. It is worth noting that all inclusion scene, spectral, and chemical characteristics, as well as the comparison presented in this study are of a limited number of samples from Tanzania and Myanmar. Full article

(This article belongs to the Special Issue Gem Characterisation)

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15 pages, 7110 KiB

Open AccessArticle

Non-Destructive Study of Egyptian Emeralds Preserved in the Collection of the Museum of the Ecole des Mines

by Maria Nikopoulou, Stefanos Karampelas, Eloïse Gaillou, Ugo Hennebois, Farida Maouche, Annabelle Herreweghe, Lambrini Papadopoulou, Vasilios Melfos, Nikolaos Kantiranis, Didier Nectoux and Aurélien Delaunay

Minerals 2023, 13(2), 158; https://doi.org/10.3390/min13020158 - 21 Jan 2023

Cited by 1 | Viewed by 1913

Abstract

In the present study, rough emerald single crystals and rough emeralds in the host rock from the ruins of Alexandria and from the Mount Zabargad in Egypt, preserved in the collection of the museum of the Ecole des Mines (Mines Paris—PSL) since the [...] Read more.

In the present study, rough emerald single crystals and rough emeralds in the host rock from the ruins of Alexandria and from the Mount Zabargad in Egypt, preserved in the collection of the museum of the Ecole des Mines (Mines Paris—PSL) since the late 19th or early 20th century, are investigated. All samples were characterized by non-destructive spectroscopic and chemical methods during a week-long loan to the LFG. Raman, FTIR and UV-Vis-NIR spectroscopy revealed that Egyptian emeralds contain H₂O molecules accompanied by relatively high concentrations of alkali ions and are colored by chromium and iron. Additionally, EDXRF showed that the emeralds from Egypt contain up to 84 ppm Rb and low amounts (below 200 ppm) of Cs. Inclusions and parts of the host rock were also observed under optical microscope and analyzed with Raman spectroscopy. Tube-like structures, quartz, calcite, dolomite, albite and phlogopite are associated minerals, and inclusions are identified in these historic emeralds from Egypt. This work will hopefully further contribute to the characterization of emeralds of archaeological significance. Full article

(This article belongs to the Special Issue Gem Characterisation)

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17 pages, 2158 KiB

Open AccessArticle

Shortwave UV Blue Luminescence of Some Minerals and Gems Due to Titanate Groups

by Maxence Vigier, Emmanuel Fritsch, Théo Cavignac, Camille Latouche and Stéphane Jobic

Minerals 2023, 13(1), 104; https://doi.org/10.3390/min13010104 - 09 Jan 2023

Cited by 4 | Viewed by 4028

Abstract

This article reviews blue shortwave-excited luminescence (BSL) in natural minerals and synthetic materials. It also describes in detail the emission of seven minerals and gems displaying BSL, as well as three references in which BSL is caused by titanate groups (TiO₆): [...] Read more.

This article reviews blue shortwave-excited luminescence (BSL) in natural minerals and synthetic materials. It also describes in detail the emission of seven minerals and gems displaying BSL, as well as three references in which BSL is caused by titanate groups (TiO₆): benitoite, Ti-doped synthetic sapphire and spinel. Emission (under 254 nm shortwave excitation) and excitation spectra are provided, and fluorescence decay times are measured. It is proposed that BSL in beryl (morganite), dumortierite, hydrozincite, pezzotaite, tourmaline (elbaite), some silicates glasses, and synthetic opals is due to titanate groups present at a concentration of 20 ppmw Ti or above. They all share a broad emission with a maximum between 420 and 480 nm (2.95 to 2.58 eV) (thus perceived as blue), and an excitation spectrum peaking in the short-wave range, between 230 and 290 nm (5.39 to 4.27 eV). Furthermore, their luminescence decay time is about 20 microseconds (from 2 to 40). These three parameters are consistent with a titanate emission, and to our knowledge, no other activator. Full article

(This article belongs to the Special Issue Gem Characterisation)

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22 pages, 9620 KiB

Open AccessArticle

A Research of Emeralds from Panjshir Valley, Afghanistan

by Quanli Chen, Peijin Bao, Yan Li, Andy H. Shen, Ran Gao, Yulin Bai, Xue Gong and Xianyu Liu

Minerals 2023, 13(1), 63; https://doi.org/10.3390/min13010063 - 30 Dec 2022

Cited by 2 | Viewed by 4521

Abstract

In recent years, emeralds from the Panjshir Valley in Afghanistan have taken a large share of the market, with high-quality emeralds comparable to Colombian emeralds. In order to meet the market demand for tracing the origin of emeralds, 20 emeralds from the region [...] Read more.

In recent years, emeralds from the Panjshir Valley in Afghanistan have taken a large share of the market, with high-quality emeralds comparable to Colombian emeralds. In order to meet the market demand for tracing the origin of emeralds, 20 emeralds from the region were tested using conventional gemology, laser Raman spectroscopy, Fourier infrared spectroscopy, ultraviolet-visible-near-infrared spectroscopy, and laser ablation plasma-mass spectrometry. The results show that the contents of the samples are mainly serrated three-phase inclusions, which are similar to those of Colombian emeralds. There are multiple solid inclusions and two liquids in the serrated voids. The main coloring elements of the sample are chromium and vanadium. The alkali metal content is moderate, among which rubidium (average content: 25.72 ppm) and cesium (average content: 33.15 ppm) content is lower. The near-infrared spectrum reveals that the absorption characteristic was dominated by type I water. A chemical composition analysis indicates that the chemical composition of Panjshir emeralds is similar to that of the emeralds of Davdar Township in China and Coscuez in Colombia, but they could be distinguished by an Na-Sc and Rb-Ga diagram. Full article

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26 pages, 15235 KiB

Open AccessArticle

Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin

by Evgeniya N. Svetova and Sergei A. Svetov

Minerals 2023, 13(1), 62; https://doi.org/10.3390/min13010062 - 30 Dec 2022

Cited by 2 | Viewed by 1759

Abstract

Agate gemstones occurring in the Mesoproterozoic volcanic rocks of the Priozersk Formation (PrF) within the Pasha–Ladoga Basin (Fennoscandian Shield, NW Russia) were investigated to characterize the mineral and geochemical composition of the agates and provide new information concerning their origin. Optical and scanning [...] Read more.

Agate gemstones occurring in the Mesoproterozoic volcanic rocks of the Priozersk Formation (PrF) within the Pasha–Ladoga Basin (Fennoscandian Shield, NW Russia) were investigated to characterize the mineral and geochemical composition of the agates and provide new information concerning their origin. Optical and scanning electron microscopy, EDS microanalysis, X-ray powder diffraction, X-ray fluorescence spectrometry, Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), and C-O isotope analysis were used for the study. Agate mineralization appears mostly as an infill of fissures, cavities, gas vesicles in massive and vesicular basalts, lava-breccias. The mineral composition of agates is dominated by alpha-quartz (fibrous chalcedony, microcrystalline and macrocrystalline quartz), but it also displays abundances of calcite. The characteristic red-brownish agate’s coloration is caused by multiple hematite inclusions distributed in an agate matrix. The study revealed the two phases of agate formation in the PrF volcanics, which are most likely controlled by two distinctly different fluids and/or their mixture. At first, agates appeared due to post-magmatic iron-rich fluids. The late hydrothermal activity was probably triggered by intrusion of gabbro-dolerite sill and resulted in the second phase of agate formation. We suggest that the late hydrothermal fluids remobilized the iron compounds from the crust of weathering underlying the PrF volcanics, which led to additional formation of vein agates and filling of gas vesicles with hematite-rich calcite/silica matter. Full article

(This article belongs to the Special Issue Gem Characterisation)

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13 pages, 10431 KiB

Open AccessArticle

The Heat Treatment of Pink Zoisite

by Clemens Schwarzinger

Minerals 2022, 12(11), 1472; https://doi.org/10.3390/min12111472 - 21 Nov 2022

Cited by 1 | Viewed by 2592

Abstract

Natural pink zoisites owe their color to a high concentration of manganese paired with low concentrations of other coloring elements such as vanadium or titanium. Upon conventional heating, such stones typically suffer from the reduction of Mn³⁺ to the colorless Mn²⁺ [...] Read more.

Natural pink zoisites owe their color to a high concentration of manganese paired with low concentrations of other coloring elements such as vanadium or titanium. Upon conventional heating, such stones typically suffer from the reduction of Mn³⁺ to the colorless Mn²⁺ species alongside the destruction of the brownish yellow color that is related to titanium. We have processed manganese containing zoisites under the high pressure of pure oxygen which allowed the manganese to remain oxidized, while the brownish yellow color component was still successfully removed. Depending on the vanadium level, the treated gems show a pink to purplish pink color. Detection of this treatment is not easy as the temperature is too low to result in a change in internal features, but a combination of UV-Vis-NIR spectroscopy and trace element chemistry provided by LA-ICP-MS give evidence of such treatment. Full article

(This article belongs to the Special Issue Gem Characterisation)

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Graphical abstract

17 pages, 6720 KiB

Open AccessArticle

Black Quartz from the Burano Formation (Val Secchia, Italy): An Unusual Gem

by Franca Caucia, Maurizio Scacchetti, Luigi Marinoni and Mattia Gilio

Minerals 2022, 12(11), 1449; https://doi.org/10.3390/min12111449 - 16 Nov 2022

Cited by 2 | Viewed by 1855

Abstract

The Burano Formation in Val Secchia in the province of Reggio Emilia is rich in black or very dark quartz. The crystals are often pitted by scars, rarely shiny, often opaque, rarely translucent, and about 3 cm long. However, they have a beautiful [...] Read more.

The Burano Formation in Val Secchia in the province of Reggio Emilia is rich in black or very dark quartz. The crystals are often pitted by scars, rarely shiny, often opaque, rarely translucent, and about 3 cm long. However, they have a beautiful color and are generally euhedral and bi-terminate with simple habitus and well developed faces—for these characteristics, they are very sought after by collectors. Micro-Raman analyses showed the quartz contains abundant inclusions of anhydrite and graphite. The inclusions of anhydrite are responsible for the chromatic inhomogeneity, while the black color is linked to the presence of disordered graphite inclusions. LA-ICP-MS analyses did not show a significant presence of chromophore elements. Black quartz formed in the original evaporite deposits of gypsum, which, due to diagenesis and the increase in temperature during deep tectonic burial conditions, lost water of crystallization and subsequently transformed into anhydrite. After the formation of quartz crystals, the Burano Formation was exhumated and rehydrated, resulting in gypsification at conditions close to the surface. The black quartzes of the Burano Formation represent an appreciable gemological material for the development of local craftsmanship, even if the difficulties in reaching the deposit limit their marketing. Full article

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13 pages, 10795 KiB

Open AccessArticle

Application of High-Temperature Copper Diffusion in Surface Recoloring of Faceted Labradorites

by Qingchao Zhou, Chengsi Wang and Andy-Hsitien Shen

Minerals 2022, 12(8), 920; https://doi.org/10.3390/min12080920 - 22 Jul 2022

Cited by 4 | Viewed by 1678

Abstract

Owing to the high market values of natural sunstones in Oregon, a kind of artificially diffused red feldspar exhibited at the Tucson Exhibition at the beginning of this century, whose color origin is the same as that of natural sunstone (copper nanoparticles). However, [...] Read more.

Owing to the high market values of natural sunstones in Oregon, a kind of artificially diffused red feldspar exhibited at the Tucson Exhibition at the beginning of this century, whose color origin is the same as that of natural sunstone (copper nanoparticles). However, the details of the artificial diffusion process are less disclosed, there is no systematic method to obtain such gemstones. In this paper, we developed the high-temperature copper diffusion process for the surface recoloring of faceted labradorites, which are partly buried in the diffusant. By optimizing the experimental parameters of high-temperature copper diffusion, we successfully recolored the faceted labradorites to red and light red. The gemological and spectroscopic characteristics of the recolored faceted labradorite were further characterized. The red and light-red faceted labradorites exhibited the unique surface plasmon resonance absorption peaks of copper nanoparticles near 580 nm, which is the origin of red color. The typical inclusions formed in the faceted labradorite is in the shape of “fire cloud”. The interface of red and light-red faceted labradorite that is in contact with the diffusant is less contaminated, we believe that the contamination could be further reduced or eliminated by optimizing the high-temperature copper diffusion process. The way that the sample is in contact with the diffusant partly is versatile and promising in the surface treatment of materials that have already been processed. Full article

(This article belongs to the Special Issue Gem Characterisation)

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Review

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15 pages, 10665 KiB

Open AccessReview

Fluorescence and Phosphorescence Spectroscopies and Their Applications in Gem Characterization

by Zhiqing Zhang and Andy Shen

Minerals 2023, 13(5), 626; https://doi.org/10.3390/min13050626 - 29 Apr 2023

Cited by 4 | Viewed by 2438

Abstract

Fluorescence and phosphorescence are listed as mineral optical–physical properties in classical gemology textbooks. The trace elements which exist in gems, certain defects in the crystal lattice, and some luminous molecules contribute to luminescence phenomena in gem materials, including fluorescence and phosphorescence. A systematic [...] Read more.

Fluorescence and phosphorescence are listed as mineral optical–physical properties in classical gemology textbooks. The trace elements which exist in gems, certain defects in the crystal lattice, and some luminous molecules contribute to luminescence phenomena in gem materials, including fluorescence and phosphorescence. A systematic luminescence study using an excitation-emission matrix (EEM) not only provides detailed information about the emission and excitation peaks, but also indicates the presence of specific trace elements, lattice defects, or luminous substances in gem materials. This provides reliable evidence for the characterization of gems. In this review paper, we briefly summarize luminescence spectroscopy and illustrate its applications in gem materials in our laboratory, including diamonds, fluorite, jadeite jade, hauyne, and amber. Meanwhile, this project is in process and needs more samples from reliable sources to confirm the described data. Full article

(This article belongs to the Special Issue Gem Characterisation)

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