Gemmology
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Tuesday, 18 June 2019


Gemmology — gemstones — characteristics, classification, specimens, library
Rhodolite

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

Epidote

— Characteristic of several facies of regionally metamorphosed rocks and some contaminated felsic igneous rocks; in contact zones between igneous and calcareous sedimentary rocks; from alteration of plagioclase (Anthony et al., 2001—2005). Faceted specimens are rare.
Epidote

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
Almandine — specimen 0632

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Bytownite — specimen 0284
Chromian pyrope — specimen 0289
Pargasite — specimen 0294
Rock crystal — specimen 0300

— 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

phonolite — a rare extrusive igneous rock, of intermediate chemical composition between felsic and mafic
phosphophyllite — species of mineral; faceted specimens exist
phosphosiderite — species of mineral; see phosphosiderite in ‘Classification’
pleochroism — оn optical phenomenon in which the gemstone appears to be different colours when observed at different angles
Publications

Anthony, J. W., Bideaux, R. A., Bladh, K. W., Nichols, M. C. (Eds), 2001—2005 — Ilmenite — Features the data of ilmenite; from ‘Handbook of Mineralogy’.
Anthony, J. W., Bideaux, R. A., Bladh, K. W., Nichols, M. C. (Eds), 2001—2005 — Hematite — Features the data of hematite; from ‘Handbook of Mineralogy’.