SYLVANITE  , a

mineral consisting of gold and silver telluride, AuAgTe4, containing gold 24.2 and silver 13.3 %; an important ore of gold . Crystals are monoclinic and often very rich in faces; they are frequently twinned, giving rise to branching forms resembling written characters; on this account the mineral was early known as " graphic gold " or " graphic tellurium " (Ger . Schrifterz) . It was also known as " white gold," the colour being tin-white with a brilliant metallic lustre . The hardness is 2 and the specific gravity 8.2 . It occurs with native gold in veins traversing porphyry at Offenbanya and Nagyag, near Deva in Transylvania (from which country it takes its name) ; also at several places in Boulder county, Colorado, and at Kalgoorlie in Western Australia . Sylvanite may be readily distinguished from calaverite (AuTez) by its perfect cleavage in one direction (parallel to the plane of symmetry), but in this character it resembles the very rare orthorhombic mineral krennerite ([Au, Ag]Tez) . (L . J .