1) Ag2s an ore mineral of silver 2) Monoclinic mineral 3) Sulfide mineral 
Acanthite, Ag2S, crystallizes in the monoclinic system and is the stable form of silver sulfide below 173 °C. Argentite is the stable form above that temperature. As argentite cools below that temperature its cubic form is distorted to the monoclinic form of acanthite. Below 173 °C acanthite forms directly. Acanthite is the only stable form in n...
a silver sulfide mineral (Ag2S) that is the most important ore of silver. It is abundant, with other silver minerals, in the sulfide mineral deposits ...
Acanthite is a mineral very similar to argentite, differing only in internal structure; the crystal of Acanthite being monoclinic - acanthite can be turned into argentite by heating. Acanthite is an important ore of silver, and forms spiky-looking crystals.
Ag2S An ore mineral of silver
the orthorhombic form of silver sulfide. Cf. argentite.