Black acanthite mass 1.2 cm long on quartz. Guanajuata, Mexico. (Image by W.S. Cordua.)

Formula: Ag2S Monoclinic


Acanthite is a low-temperature hydrothermal mineral. It can form from inversion of argentite, a mineral that forms in higher temperature hydrothermal deposits.

ONEIDA COUNTY: Acanthite occurs with gold, silver and other silver minerals in the Lynn massive sulfide deposit. Galena, sphalerite, and chalcopyrite are the major ore minerals in this deposit (Kennedy et al., 1991).