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Sunday, 22 October 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 163 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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— Common in the oxidised zone of lead deposits, where it may constitute an important ore (Anthony et al., 2001—2005). Faceted specimens are very rare. The largest faceted stone is a 408 carat from Tsumeb, Namibia (Arem, 1987: 64).

The section ‘Repository’ contains data and photos of 728 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
Indicolite — specimen 0329
Indicolite — specimen 0330
Amethyst — specimen 0336
Indicolite — specimen 0338

— 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 381 terms.

diaspore — species of mineral; see diaspore in ‘Classification’
dike — a sheet of rock that formed in a crack in a pre-existing rock body
diopside — species of mineral; see diopside in ‘Classification’
dodecagon — rare shape in faceting a gemstone

Anthony, J. W., Bideaux, R. A., Bladh, K. W., Nichols, M. C. (Eds), 2001—2005 — Allanite-(Ce) — Features the data of allanite-(Ce); from ‘Handbook of Mineralogy’.
Klaproth, M. H., 1802 — Chemische Untersuchung des Gadolinits — Published in 1802 in ‘Beiträge zur Chemischen Kenntniss der Mineralkörper’; contains the original description of the mineral gadolinite-(Y).