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Friday, 18 June 2021

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 171 different kinds of natural gemstones (106 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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— Characteristic of several facies of regionally metamorphosed rocks and some contaminated felsic igneous rocks; in contact zones between igneous and calcareous sedimentary rocks; from alteration of plagioclase (Anthony et al., 2001—2005). Faceted specimens are rare.

The section ‘Repository’ contains data and photos of 760 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 8 specimens of synthetic stones.

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Andesine — specimen 0305

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Agate — specimen 0371
Agate — specimen 0372
Cordierite — specimen 0380
Cordierite — specimen 0381

— More from ‘Repository

Currently there are 283 bibliographical references and abstracts to publications with gemmological or mineralogical thematics in the ‘Library’. The section comprises also a glossary with 391 terms.

grandidierite — species of mineral; see grandidierite in ‘Classification’
grandite — synonym of grossular-andradite series
granite — a common type of intrusive, felsic, igneous rock which is granular in texture
green beryl — variety of beryl; see green beryl in ‘Classification’

Haüy, R. J., 1801 — VII. Diaspore (m.), c’est-à-dire, qui se disperse — Published by Haüy in 1801 in ‘Traité de Minéralogie’; contains the original description of the mineral diaspore.
Gehlen, A. F., Fuchs, J. N., 1813 — Ueber Werner’s Zeolith, Hauy’s Mesotype und Stilbite — Published in 1813 in ‘Journal für Chemie und Physik’; contains the original description of the mineral scolecite.