These acanthite crystals are from the San Juan de Rayas Mine in Guanajuato, Mun. de Guanajuato, Guanajuato, Mexico. This is a gold and silver mine that contains 16 different minerals including acanthite. It is a silver sulfide containing the elements Ag and S. This piece consists of a cluster of acanthite crystals with minor calcite attached.The crystals have pseudo-cubic and pseudo-octahedral habits. Some have hoppered or skeletal habits. They have a silver-grey color, stair step crystal faces and a metallic luster. This piece measures 27 x 16 x 12 mm.