tə̇.ˈtradəˌmīt noun
( -s )
Etymology: Late Greek tetradymos fourfold, from Greek tetra- + didymos twin; from its occurrence in compound twin crystals — more at -dymus
: a mineral Bi 2 Te 2 S consisting of a telluride and sulfide of bismuth, sometimes containing selenium, being pale steel gray in color and of a metallic luster, and occurring usually in foliated masses (hardness 1.5-2, specific gravity 7.2-7.6)