These cuprite crystals are from the Milpillas Mine in Cuitaca, Mun de Santa Cruz, Sonora, Mexico. Mining at this locale began in 2006 with the extraction of copper minerals. Thirty-six mineral species have been identified at the mine including cuprite. It is a secondary mineral found in oxidized copper ore bodies and it contains the elements Cu, C and O. Mining started in several copper oxide zones where outstanding secondary copper mineral specimens were recovered. This specimen consists of a quartz matrix (sawed on the rear surface) that hosts several large well defined cuprite crystals. The cuprites are octahedral to complex and their luster is mirror like. This piece measures 2 1/2 x 1 3/8 x 5/8 inches or 64 x 35 x 16 mm.