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Friday, 28 April 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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— Also known as sphene; a common accessory mineral in intermediate and felsic rocks, pegmatites, and alpine veins; in gneisses, schists, and some skarns (Anthony et al., 2001—2005).

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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Rhodolite — specimen 0660

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Zircon — specimen 0212
Hyacinth — specimen 0221
Opal — specimen 0227
Malaia garnet — specimen 0230

— 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.

pyroclastics — clastic rocks composed solely or primarily of volcanic materials
pyrope — species of mineral; see pyrope in ‘Classification’
pyrope-almandine series — a series between pyrope and almandine; see pyrope-almandine series in ‘Classification’
pyrope-spessartine series — a series between pyrope and spessartine; see pyrope-spessartine series in ‘Classification’

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’.