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Tuesday, 21 February 2017

Gemmology — gemstones — characteristics, classification, specimens, library


characteristics, classification, specimens, library

As gemstones we accept cut specimens of crystals of natural mineral species having a visible transparency and certain durability. From over 4800 known minerals (according to data of the International Mineralogical Association), approximately 150 satisfy the above conditions and form crystals of sufficient size to be cut.

The section ‘Classification’ presents descriptions of 162 different kinds of natural gemstones (104 mineral species). The Nickel-Strunz systematic order (10th edition) is used. Since gemmology does not always follow the systematics of minerals in naming, many popular varieties or just ’names’ are listed.

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— Produced by regional or contact metamorphism of magnesium carbonate, mafic, or ultramafic rocks (Anthony et al., 2001—2005). Faceted specimens are extremely rare.

The section ‘Repository’ contains data and photos of 670 specimens of gemstones. The smallest is just 1.96 mm (0.02 ct) ruby from Mozambique, and the largest — 70.11 mm (326.60 ct) rock crystal from Africa. Besides there are 7 specimens of synthetic stones.

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Kornerupine — specimen 0644

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Variscite — specimen 0076
Variscite — specimen 0077
Rose quartz — specimen 0079
Petschite — specimen 0081

— More from ‘Repository

Currently there are 279 bibliographical references and abstracts to publications with gemmological or mineralogical thematics in the ‘Library’. The section comprises also a glossary with 380 terms.

granite — a common type of intrusive, felsic, igneous rock which is granular in texture
green beryl — variety of beryl; see green beryl in ‘Classification’
greisen — a highly altered granitic rock or pegmatite
grossular — species of mineral; see grossular in ‘Classification’

von Leonhard, K. C., 1821 — Scheelit — Published in 1821 in ‘Handbuch der Oryktognosie’; contains the original description of the mineral scheelite.
Anthony, J. W., Bideaux, R. A., Bladh, K. W., Nichols, M. C. (Eds), 2001—2005 — Uvite — Features the data of uvite; from ‘Handbook of Mineralogy’.