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Andradite (var. demantoid)

Rough crystal and two gems: 6.96ct oval and 3.00ct cushion cut demantoids.
Photo by Ken Larsen. Click to zoom.
Catalog Number NMNH G11480-00
Locality Green Dragon mine, Erongo, Namibia
Weight 6.96 ct

Purchased with funds from the Tiffany & Co. Foundation in 2014.

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 F. Kunz, the chief gemologist 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. Demantoid 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. This 6.96ct oval gem (left) is from the Green Dragon Mine in Namibia and exhibits a medium dark yellowish-green color. Also in the photo are a 3.00ct cushion cut gem (right) and a rough crystal specimen (center).


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