Demantoid
About Demantoidextended article
Demantoid is the green gem variety of andradite, a calcium-iron garnet. Its name comes from its 'diamond-like' fire: andradite has a very high dispersion that, in transparent green stones, produces flashes of spectral colour rivalling diamond. The green is caused by chromium, with iron lending more yellowish tones.
Properties
Like all garnets it is isometric, singly refractive, hard (6.5–7) and cleavage-free. Russian demantoid is famous for fine fibrous 'horsetail' inclusions of chrysotile radiating from a central point — a feature unique to that source and accepted as a mark of origin rather than a flaw.
Occurrence
The original and most celebrated demantoid comes from the Ural Mountains of Russia; important later finds include Namibia (the Erongo region's Green Dragon material) and Iran, Madagascar and Italy. It is the most valuable member of the andradite garnet species.
Frequently asked questions
What is the chemical formula of Demantoid?
The chemical formula of Demantoid is Ca3Fe2(SiO4)3.
What crystal system does Demantoid belong to?
Demantoid crystallises in the Isometric crystal system.
Where is Demantoid found?
Notable localities for Demantoid include Ural Mountains, Val Malenco.
Is Demantoid rare?
As a collector mineral, Demantoid is generally considered rare.
References & databases
Mindat.org is the world’s largest open mineralogy database. Our descriptions are written independently and fact-checked.