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Friday, 24 November 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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— The most abundant rare earth elements-bearing mineral, typically hydrothermal, although primary igneous occurrences are known; in granite and alkali syenites and pegmatites; in carbonatites (Anthony et al., 2001—2005). Faceted specimens are very rare.

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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Amethyst — specimen 0706

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Hyacinth — specimen 0221
Opal — specimen 0227
Malaia garnet — specimen 0230
Danburite — specimen 0234

— 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.

Mali garnet — synonym of grandite; grossular-andradite series
marble — a rock; see marble in ‘Classification’
marialite — species of mineral; see marialite in ‘Classification’
marialite-meionite series — a series between marialite and meionite; see marialite-meionite series in ‘Classification’

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.
Schmetzer, K., Bernhardt, H.-J., 1999 — Garnets from Madagascar with a Color Change of Blue-Green to Purple — The paper features the gemological, chemical, spectroscopic, and microscopic properties of blue-green colour change garnets from a deposit near Bekily, Madagascar. Specimens from this locality exist in ‘Repository’.