These mimetite crystals are from the Ojuela Mine in Mapimi, Durango, Mexico. There a over 115 different types of minerals in the mine including mimetite. It is an arsenate that contains the elements Pb, As, O and Cl. This specimen consists of a limonite/goethite matrix that hosts mound-like formation of cauliflower shaped clusters of mimetite crystals. This piece measures 3 1/4 x 2 x 2 inches or 83 x 50 x 50 mm.