Friday, 19 May 2017

Demantoid Garnet

Demantoid is the green gemstone variety of andradite, a member of the garnet group. Andradite is a calcium-and iron-rich garnet with the formula Ca3Fe2(SiO4) with chromium the cause of the demantoid green color. Ferric iron is the cause of the yellow in the stone. Demantoid garnet was first discovered in 1886 and became a favorite of Russian royalty and designer Carl Fabergé, who incorporated them into his jewelry.
Russian mining of demantoid garnet was suspended after the Bolshevik Revolution in 1917, but resumed in the 1970s.
Demantoid gets its name from the Dutch words for “diamond-like.” The stone owes its impressive brilliance to two main factors: A high refractive index and a high dispersion. Demantoid’s dispersion rating is the highest of all gemstones, including diamond. Known for their brilliant green color and fiery dispersion, demantoid garnets are unique because their inclusions — usually seen as flaws in other gems — are considered highly coveted aesthetic attributes.
Demantoid garnet is mined in other parts of the world, including Iran, Namibia, Pakistan, Italy, Madagascar and Canada, but Russian demantoid sets the mark by which all the others are compared. Demantoid garnets are rarely found in sizes larger than 2 carats.