This is a specimen of dioptase from Tsumeb, Namibia. Dioptase is a type of hydrated silicate of copper. The cluster of intergrown crystals in this specimen have highly vitreous faces and sit upon an aesthetic matrix, which has small spots of light-green where trace amounts of dioptase crystals lie.
This specimen is approximately 45mm x 35mm x 25mm. You will also receive a mineral card with the specimen name and the locale where it was mined.