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Sunday, 5 April 2020

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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— 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 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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Simple colour schemeredorangey redreddish orangeorangeorangey yellowyellowgreenish yellowyellowish greenslightly yellowish greengreenvery slightly bluish greenbluish greenvery strongly bluish greengreen-blue or blue-greenvery strongly greenish bluevery slightly greenish bluebluevioletish bluebluish violetvioletbluish purplepurplereddish purplestrongly purplish redslightly purplish redcolourlessgreyblack
Hyacinth — specimen 0516

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Ruby — specimen 0276
Bytownite — specimen 0284
Chromian pyrope — specimen 0289
Pargasite — specimen 0294

— 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.

amblygonite — species of mineral; see amblygonite in ‘Classification’
amethyst — variety of quartz; see amethyst in ‘Classification’
ametrine — variety of quartz; see ametrine in ‘Classification’
amphiboles — an extensive and complex group of minerals

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’.