1911 Encyclopædia Britannica/Sylvanite

by Leonard James Spencer

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 tellerium" (German 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 trasversing porphyry at Offenbánya and Nagyág, near Déva 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 (AuTe₂) 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] Te₂).

(L. J. S.)