Demantoid

Demantoid is a very beautiful green variety of garnet that was first discovered in the Ural Mountains of Russia.

Some Russian demantoid is highly prized for containing unique horsetail inclusions.  Unlike diamonds, which become less valuable with large inclusions, demantoid with horsetail inclusions are more valuable than those without!

Other sources of demantoid include Namibia, Madagascar, as well as other locations worldwide.