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— A late phase in nepheline syenites, syenitic pegmatites, and along the contact zone of a differentiated alkalic massif (Lovozero Massif, Russia) (Anthony et al., 2001—2005). Faceted specimens are extremely rare.

Specimen figured

Vlasovite — specimen 0006weight: 0.22 ct; shape: cushion triangle. Very clean specimen; very good brilliant style cut. The specimen is from the series mentioned by Overlin, 2012. Source: John Bradshaw, Coast to Coast Rare Stones International.


The section ‘Classification’ presents descriptions of 171 different kinds of natural gemstones (106 mineral species). The Nickel-Strunz systematic order (10th edition) is used. Specimens of the classes shown below are currently available. Since gemmology does not always follow the systematics of minerals in naming, many popular varieties or just ’names’ are also listed.

Classes after Nickel-Strunz

1. Elements
2. Sulphides & sulphosalts
3. Halides
4. Oxides & hydroxides
5. Carbonates (Nitrates)
6. Borates
7. Sulphates
8. Phosphates, arsenates, vanadates
9. Silicates


— 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.

Specimen figured

Cordierite — specimen 0214weight: 0.18 ct; shape: oval. Very clean specimen; good mixed style cut. Source: Gary Eisenberg, Knoxville, Tennessee.
Cordierite — specimen 0214