Gemmology
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Wednesday, 11 December 2019


Gemmology — gemstones — characteristics, classification, specimens, library
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GEMMOLOGY — GEMSTONES

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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Classification
Featured

Cordierite

— In thermally metamorphosed argillaceous sediments and regionally metamorphosed schists, gneisses; in mafic igneous rocks and granites (Anthony et al., 2001—2005). The gemstone bears the name iolite.
Cordierite

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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Repository
Heliodor — specimen 0497

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Chrysoberyl — specimen 0166
Opal — specimen 0167
Johachidolite — specimen 0174
Jadeite — specimen 0200

— 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.
Library
Glossary

diabase — a mafic, subvolcanic rock; equivalent to volcanic basalt
diagenesis — the change of sediment or existing sedimentary rocks into sedimentary rock during and after rock formation, at temperatures and pressures less than that required for the formation of metamorphic rocks
diamond — species of mineral; see diamond in ‘Classification’
diaspore — species of mineral; see diaspore in ‘Classification’
Publications

Anthony, J. W., Bideaux, R. A., Bladh, K. W., Nichols, M. C. (Eds), 2001—2005 — Antigorite — Features the data of antigorite; from ‘Handbook of Mineralogy’.
Anthony, J. W., Bideaux, R. A., Bladh, K. W., Nichols, M. C. (Eds), 2001—2005 — Friedelite — Features the data of friedelite; from ‘Handbook of Mineralogy’.