Matrix specimens of acanthite are much more difficult to find than loose crystals. These crystals, up to 6 mm on edge, are intergrown with nicely contrasting crystals of white dolomite. The piece measures 33 x 32 x 20 mm. A wonderful large thumbnail that I purchased many years ago in the town of Guanajuato which is located in the state of Guanajuato, Mexico.