Pink to Pinkish Orange Malaya Garnets from Bekily, Madagascar

Schmetzer, Karl; Hainschwang, Thomas; Kiefert, Lore; Bernhardt, Heinz-Jürgen

doi:10.5741/gems.37.4.296

Cited by 12 publications

(21 citation statements)

References 14 publications

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“…The amount of aluminium(III) found during the analysis varies from 20.20 to 36.37%, calcium oxide from 22.26-26.93, silicon(IV) oxide from 33.52-52.46% and iron(III) oxide about 0.64%. the range from 3.54 to 3.63 g/cm 3 and are in a good agreement with the literature data. The specific gravity of the dark green, medium green and light green tsavorites are 3.62, 3.66 and 3.61 g/cm 3 , respectively.…”

Section: Fig 11 Colourless Grossular (India) Photo By Irzhi Kornsupporting

confidence: 92%

“…The hardness according to the Mohs scale is 7-7.5, the density 3.84 (+/-0.10) and the refractive index 1.760 (+0.010-0.020). The absorption spectra typically have absorption maxima at 504, 520 and 573 nm, and may also have a weak line at 423, 460, 610 and 680-690 nm [3]. Rhodolite is a mixture of pyrope and almandine.…”

Section: Fig 3 Almandine (India) Photo By I Balčiūnaitėmentioning

confidence: 99%

“…Its beauty is defined primarily by its colour: orange, red-orange and yellow-brown. Gloss is glassy, the refractive index 1.79-1.82, the density 4.12-4.20 g/cm 3 and the hardness 7-7.5 [2]. After the determination of chemical elements in spesartine, it was found out that the content of manganese(II) oxide varies from 34.70 to 36.59% and that of aluminium(III) oxide from 21.43 to 23.13%, which are characteristic of spessartine and its varieties.…”

Section: Fig 3 Almandine (India) Photo By I Balčiūnaitėmentioning

confidence: 99%

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Characterization of natural silicate garnets by means of non-destructive testing methods

Balčiūnaitė¹,

Ignatjev²,

Kaminskas³

et al. 2021

chemija

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Two kinds of natural silicate garnets from the known origin countries were investigated: pyralspites – pyrope (Russia), almandine (India), rhodolite (India), spessartine (India), blue colour-change garnet (Sri Lanka), and ugrandites – andradite (Russia), demantoid (Russia), topazolite (Russia), rainbow garnet (Japan), grossular (Kenya-Tanzania), colourless grossular (India), light orange grossular (India), dark green tsavorite (Tanzania), medium green tsavorite (Kenya), light green tsavorite (Kenya), orange hessonite (Sri Lanka), pink hessonite (Sri Lanka), cinnamon hessonite (India) and uvarovite (Russia). The chemical composition of the garnets was performed with a scanning electron microscope. The physical properties such as specific gravity and refractive index were measured for the majority of garnets investigated. The spectroscopic methods – visible light absorption spectrophotometry, Raman spectroscopy and cathodoluminiscence microscopy – were applied for the characterization of the mentioned natural silicate garnets.

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Section: Fig 11 Colourless Grossular (India) Photo By Irzhi Kornsupporting

confidence: 92%

Section: Fig 3 Almandine (India) Photo By I Balčiūnaitėmentioning

confidence: 99%

Section: Fig 3 Almandine (India) Photo By I Balčiūnaitėmentioning

confidence: 99%

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Characterization of natural silicate garnets by means of non-destructive testing methods

Balčiūnaitė¹,

Ignatjev²,

Kaminskas³

et al. 2021

chemija

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“…The compositions of garnets lying in the pyralspite range (see Table Ia and Figure 2), namely pyrope (variety chrome pyrope), almandine, pyrope-almandine (variety rhodolite), spessartine and almandinespessartine are consistent with those in the literature (Deer et al, 1997;Eeckhout et al, 2002). The pyrope-spessartine variety known by some in the gem trade as 'malaya garnet' contains 52.75 mol.% pyrope, 33.65 mol.% spessartine, 6.10 mol.% grossular and 7.50 mol.% almandine (sample 9), which is consistent with results reported by Schmetzer et al (2001), and shows just small contents of Cr 3+ and V 3+ . The chromatic behaviour of the colour-change pyropespessartine (sample 10) from green in day/ fluorescent light to purple in incandescent light, is attributable to a relatively high combined V 2 O 3 + Cr 2 O 3 content of 1.58 wt.…”

Section: Chemical Compositionsupporting

confidence: 88%

Formation of large synthetic zincite (ZnO) crystals during production of zinc white

Nowak¹,

Braithwaite²,

Nowak³

et al. 2007

Journ of Gemm

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Remarkable zincite crystals have formed as a by-product of zinc white production in Olawa Foundry, Poland. Some are of gem quality and have been faceted. Small primary crystals formed by reaction of zinc vapour with carbon dioxide from fuel burning gases leaking through faults in a diaphragm of a retort furnace. Some of these have undergone carbon monoxide-promoted and zinc vapour-assisted sublimation to form large secondary crystals. Many of these crystals are brightly coloured and transparent, and have been found up to 2 kg in weight. Most of the crystals are fluorescent in ultraviolet light.

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“…Research starting around the late 1970s demonstrated that natural largely pyrope-spessartine garnets 24 (and nearly ternary pyrope-spessartine-almandine compositions), though rare, do occur in nature (Table 1). Interestingly, they are often referred to as color change garnets that are typically characterized by pink to pinkish orange colors (Schmetzer et al 2001), but in a few instances they may have a blue-green (e.g., Schmetzer and Bernhardt 1999) or even a deeper blue color in daylight. 25 Localities for these garnets are in East Africa (Umba mining region), Sri Lanka, and Madagascar.…”

Section: Conclusion: the Pyralspite-(u)grandite And Other Garnet Clasmentioning

confidence: 99%

A tale of two garnets: The role of solid solution in the development toward a modern mineralogy

Geiger

2016

American Mineralogist

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This article reviews the development of mineralogy as a science by focusing largely on the common silicate garnets of general formula {X 3 }[Y 2 ](Si 3)O 12. It tells of important discoveries, analyses, and proposals by various scientists relating to crystallography, crystal structures, isomorphism, and solid solution starting in Europe in the late 1700s. The critical recognition of the importance of ionic size of atoms in determining crystal-chemical properties and solid-solution behavior is emphasized. The two garnet species "pyralspite" and "(u)grandite," which were considered to represent two independent solid-solution series, were introduced by N.H. Winchell and A.N. Winchell (1927) in their well-known book Elements of Optical Mineralogy. Critical comments on the assumptions behind the classification scheme have been pointed out for at least 50 yr, but it remains in use. There is more, though, behind this garnet classification scheme than just simple terminology. There are a long series of scientific discoveries and advances that are largely forgotten by the broader mineralogical community. They begin, here, with the work of the "father of crystallography," René-Just Haüy, concerning the microscopic nature of crystals around 1780 and include later discoveries and proposals by Mitscherlich, Beudant, Wollaston, and Kopp relating to isomorphism and solid-solution behavior all before 1850. A second key era started with the discovery of X-ray diffraction in 1912 that allowed the atomic structures of crystals and, furthermore, atomic and ion radii to be determined. In terms of isomorphism and solid solution, the proposals and studies of Vegard, Zambonini, Wherry, A.N. Winchell, and the "father of crystal chemistry" Goldschmidt are briefly discussed. The recognition of the sizes of atoms and ions, along with an understanding of chemical bonding behavior in crystals, was critical in the establishment of what can be termed "modern mineralogy," a quantitative science as it is largely understood today that emerged by the mid-1930s. The silicate garnet system pyrope-almandine-spessartine-grossularandradite-uvarovite shows extensive homovalent substitutional solid solution over two structural sites and complete compositional variation between "pyralspite species" and "ugrandite species" has been documented. Thus, the prerequisites behind the terms "pyralspite" and "(u)grandite," as originally formulated and often accepted even today, are incorrect and use of this classification is not recommended. Diffraction determinations of the volumes of garnet end-members and volumes of mixing of garnet solid solutions give physical insight into solid-solution behavior. Today, investigations of local structural and crystal-chemical properties, together with determinations of lattice strain and thermodynamic mixing properties, of silicate solid solutions are leading to an ever more quantitative understanding of mineral behavior from the microscopic to macroscopic level.

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Pink to Pinkish Orange Malaya Garnets from Bekily, Madagascar

Cited by 12 publications

References 14 publications

Characterization of natural silicate garnets by means of non-destructive testing methods

Characterization of natural silicate garnets by means of non-destructive testing methods

Formation of large synthetic zincite (ZnO) crystals during production of zinc white

A tale of two garnets: The role of solid solution in the development toward a modern mineralogy

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