Many people do not realize that, despite the mental association of fine dioptase with Tsumeb in Namibia because of a flood of good specimens in the 1970s, the type locality was actually an old, Russian mine some 200 years ago. Truly outstanding Russian dioptase specimens are not as common as Tsumeb pieces, to this day. This one is really about as good as you can get for a Russian dioptase. This piece has sharp crystals to 1.3 cm, some of them doubly-terminated. The calcite association provides some contrast, and the piece overall has a good 3-dimensionality to it.