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Tuesday, 12 December 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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— 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.

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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Pyrope-almandine series — specimen 0005

Some exceptional specimens of gemstones from our ‘Repository’

More specimens of gemstones
Indicolite — specimen 0043
Milky quartz — specimen 0044
Malaia garnet — specimen 0048
Hyacinth — specimen 0051

— 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.

nickeloan magnesite — variety of magnesite; see nickeloan magnesite in ‘Classification’
nifontovite — species of mineral; faceted specimens exist
nonagon — rare shape in faceting a gemstone
nuummite — an unapproved name; metamorphic rock found in Greenland, consisting primarily of two species of amphiboles — anthophyllite and gedrite; ornamental stone; sometimes spelled ‘nuumite’

Haüy, R. J., 1792 — De l’Euclase — Published in 1792 in ‘Observations sur la Physique, sur l’Histoire Naturelle et sur les Arts’; contains the original description of the mineral euclase.
Henry, D. J., Novák, M., Hawthorne, F. C., Ertl, A., Dutrow, B. L., Uher, P., Pezzotta, F., 2011 — Nomenclature of the tourmaline-supergroup minerals — Published in 2011 in ‘American Mineralogist’; contains the redefinition of the mineral uvite.