Argentite was primarily treated as a mineral belonging to the galena group, cubic silver sulfide (Ag2S), occasionally found as uneven cubes and octahedra, but more often as dendritic or earthy masses, with a blackish lead-grey color and metallic lustre. All these forms are structurally not argentite, but its monoclinic polymorph, acanthite. Due to instability in normal air temperature, the IMA commission decided to reject this mineral, which now is a discredited mineral species.
The cubic cleavage, which is so prominent a feature in galena, here present only in traces. The mineral is perfectly sectile and has a shining streak; hardness 2.5, specific gravity 7.2-7.4. It forms an important ore of silver. The mineral was mentioned 1529 by G. Agricola, but the name argentite (from the Lat. argentum, silver) was not used till 1845 and is due to W. Haidinger. Old names for the species are Glaserz, silver-glance and vitreous silver.