Characterisation of Pink-to-Red Spinel from Four Important Localities

Chankhantha, Chawalit; Amphon, Ratthaphon; Rehman, Habib ur; Shen, Andy H.

doi:10.15506/jog.2020.37.4.393

Cited by 5 publications

(8 citation statements)

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“…Occasionally, the oriented long or short needles presented iridescence under fiber optic illumination (Figure 4c,d). As previously mentioned by Chankhantha (2021) and Schmetzer (1992) [30,31], these needles or particles were possibly caused by the exsolution of högbomite, giving samples a somewhat cloudy appearance. Since Tanzanian spinels formed in marbles, it was not surprising to find abundant carbonates as the most common mineral inclusions.…”

Section: Inclusionsmentioning

confidence: 52%

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

Wu¹,

Sun²,

Ma³

et al. 2023

Minerals

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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.

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Section: Inclusionsmentioning

confidence: 52%

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

Wu¹,

Sun²,

Ma³

et al. 2023

Minerals

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“…The spinel deposits in Vietnam are mainly found in the Luc Yen area in the northern Yen Bai Province, around the Cenozoic Day Nui Con Voi metamorphic zone and the Red River shear zone (Figure 2b) [31]. The amphibolite facies metamorphism occurred in this area, with a metamorphic temperature and metamorphic pressure of 780 °C and 7 kbar, respectively [32]. The area contains three types of typical deposits with economic value, namely, metamorphic-metasomatic deposit, magmatic pegmatite deposit, and alluvial placer.…”

Section: Luc Yen Vietnammentioning

confidence: 93%

“…The clear octahedral outline (Figure 6a) and colorless transparent short columnar inclusion with relatively complete crystal shape and clear edges (Figure 6b) can be seen. The presence of dislocation systems is the most striking inclusion feature of spinels from Luc Yen [32,49]. These dislocation systems appear as intersecting bands of iridescent parallel-oriented channels (Figure 7a) in Vietnamese spinel V-2.…”

Section: Gemstone Microscopic Observationmentioning

confidence: 99%

Characterization of Red, Pink, Orange, and Purple Gem-Quality Spinel from Four Important Areas

Xu,

Gao

et al. 2023

Crystals

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Spinel is a precious stone with a long history. In ancient societies spinel was considered to be an imitation of ruby. With the depletion of ruby mineral resources, gem—grade spinel has attracted more and more attention from consumers. In the last decade, as the popularity of spinel in the global colored gem market continues to rise, plenty of domestic and foreign jewelry brands have launched spinel based jewelry. This study takes spinels from Burma, Vietnam, Sri Lanka, and Tanzania as its research objects and performs a series of tests to obtain their gemological characteristics, spectral characteristics, and chemical composition, with the aim of comparing the differences between spinels with different colors from different areas and exploring the chromogenic mechanism of spinels. Only Burmese red spinels have a typical Cr spectrum. The types of inclusions and the contents of trace elements are the main differences between spinels from the four areas. Burmese spinel is characterized by an octahedral negative crystal filled with dolomite or a mixture of dolomite and calcite. Magnesite is present in Sri Lankan spinels, and dolomite is present in Tanzanian spinel. Dislocation systems and the presence of titanite and talc inclusions are strongly indicative features of Vietnamese spinel. Sri Lankan spinel is characterized by abundant gas–liquid inclusions, such as the beaded healing fissure. The trace element contents of the four areas are different. Burmese spinel is poor in Fe and Zn (Fe: 135.68–3925 ppm; Zn: 338.58–1312 ppm), while Burmese red spinel is rich in Cr (up to 7387 ppm). Vietnamese spinel is rich in Fe (3669.63–19,425 ppm) and poor in Ti content (<89 ppm), while Tanzanian spinel is rich in Zn (5129.96–7008 ppm). High content of Cr + V can lead to the red color in spinel, and the contents of Cr and V change obviously with color. Spinels appear red when Cr content is higher than V, while spinels appear orange when V content is higher than Cr. The red, pink, and orange spinels are colored by Cr3+ and V3+, showing a wide absorption band centered at 400 nm and 550 nm. Fe plays a dominant role in purple spinels. The purple spinel is colored by Fe3+ and Fe2+.

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“…Tanzania has been known for producing various gems for decades [31], such as rubies from Winza and Longido [32,33], sapphires from Umba Valley [34], spinels from Mahenge [35,36], tsavorite garnet [37,38], alexandrite [39], and tazanite. Cabochon-quality rubies have been discovered in the Longido area for over half a century.…”

Section: Introductionmentioning

confidence: 99%

Ruby from Longido, Tanzania: Mining, Color, Inclusion, and Chemical Features

Gao,

He,

Lucas

et al. 2024

Crystals

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This article reports on the recent mining and production status of ruby in Longido, Tanzania. Faceted-grade rubies and their matrix from Longido Area, Tanzania, were investigated by standard gemological testing, including FTIR, UV-VIS, Raman spectra, and LA-ICP-MS. Microscopic observations revealed dense needle-like and triangular inclusions, distinct growth lines, and color banding as typical inclusions. In agreement with the Raman results, the transmission FTIR spectrum confirmed the presence of aluminum hydroxide. The Raman spectra identified associated minerals and inclusions, including zoisite, parasites, feldspar within the matrix, rutile, and diaspore in the ruby host. The chemistry analysis revealed a high amount of Cr and relatively low iron as a good indicator of geographic origin.

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Characterisation of Pink-to-Red Spinel from Four Important Localities

Cited by 5 publications

References 0 publications

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

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

Characterization of Red, Pink, Orange, and Purple Gem-Quality Spinel from Four Important Areas

Ruby from Longido, Tanzania: Mining, Color, Inclusion, and Chemical Features

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