Smithsonian National Museum of Natural History
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Andradite (var. demantoid)

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Photo by Chip Clark. Click to zoom.
SpecimenCatalog NumberLocalityWeight
Andradite (var. demantoid)NMNH G3627-00Urals, Russia3.4 ct
Andradite (var. demantoid)NMNH G2175-00Urals, Russia10.4 ct
Andradite (var. demantoid)NMNH G2150-00Urals, Russia4.1 ct

Obtained in an exchange in 1961.

The rarest and most valuable garnet gem is the green to yellowish-green variety of the mineral andradite, called demantoid.  Demantoid was first discovered in Russia’s Ural Mountains in 1851, and from that time through the early 1900s they were popular in Russia and used in the finest jewelers’ workshops, often seen in Carl Fabergé’s jewelry and precious objects made for the Czars. Tiffany & Co. also made extensive use of demantoid gems in its jewelry during this period, as George Kunz, the chief gem buyer for the company, was fascinated by the gem and purchased all the rough he could find. Demantoid means “diamond like,” and the gem displays an adamantine luster with amazing brilliance and dispersion.  Gems larger than a few carats are extremely rare.  Dematoid gems are usually high in clarity but may contain characteristic inclusions of byssolite, needle-like radiating inclusions referred to as “horsetails.” Today, because of limited supplies, demantoid maintains its status as a rare and valuable gem.  Demantoid has been found in Italy and Iran, and more recently Namibia (1996). However, the Russian material continues to be the standard by which the gem is judged. The three gems pictured are a 3.4ct cushion cut, a 10.4ct cushion cut, and a 4.1ct pear-shape, all from Russia.

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