STEPHANITE  , a

mineral consisting of silver sulphantimonite, AgsSbS4; containing 68.s % of silver, and sometimes of importance as an ore of this metal . Under the name Schwarzerz it was mentioned by G . Agricola in 1546, and it has been variously known as "black silver ore" (Ger . Schwarzgultigerz), brittle silver-ore (Sprodglanzerz), &c . The name stephanite was proposed by W . Haidinger in 1845 in honour of the archduke Stephan of Austria; French authors use F . S . Beudant's name psalurose (from the Greek i1saOvp6s, fragile) . It frequently occurs as well-formed crystals, which are orthorhombic and occasionally show indications of hemimorphism: they have the form of six-sided prisms or flat tables terminated by large basal planes and often modified at the edges by numerous pyramid-planes . Twinning on the prism-planes is of frequent occurrence, giving rise to pseudo-hexagonal groups like those of aragonite . The colour is iron-black, and the lustre metallic and brilliant; on exposure to light, however, the crystals soon become dull . The mineral has a hardness of 21 and is very brittle; the specific gravity is 6.3 .

Stephanite occurs with other ores of silver in metalliferous

veins . Localities which have yielded good crystallized specimens are Freiberg and Gersdorf near Rosswein in Saxony, Chanarcillo in Chile, and exceptionally Cornwall . In the Comstock lode in Nevada massive stephanite and argentite are important ores of silver . (L . J .