ARGYRODITE  , a

mineral which is of interest as being that in which the element germanium was discovered by C . Winkler in 1886 . It is a silver sulpho-germanate, Ag8GeS6, and crystallizes in the cubic system . The crystals have the form of the octahedron or rhombic dodecahedron, and are frequently twinned . The botryoidal crusts of small indistinct crystals first found in a silver mine at Freiberg in Saxony were originally thought to be monoclinic, but were afterwards proved to be identical with the more distinctly developed crystals recently found in Bolivia . The colour is iron-black with a purplish tinge, and the lustre metallic: There is no cleavage; hardness 21, specific gravity 6.2 . It is of interest to note that the Freiberg mineral was long ago imperfectly described by A . Breithaupt under the name Plusinglanz, and that the Bolivian crystals were incorrectly described in 1849 as crystallized brongniardite . The name argyrodite is from the Greek apyupWhrls, rich in silver . Isomorphous with argyrodite is the corresponding tin compound AgsSnS6, also found in Bolivia as cubic crystals, and known by the name canfieldite . Other Bolivian crystals are intermediate in composition between argyrodite and canfieldite . (L .

J .