Emplectite forms in hydrothermal veins with other bismuth and copper minerals. Unfortunately emplectite is a difficult mineral to distinguish from other gray, acicular to massive, dense sulfosalts with a black streak. Chalcostibite has a formula of CuSbS 2 . Color is iron gray, yellow gray, whitish gray to tin white. Luster is metallic.
Crystals are opaque.
Streak is black. Specimens will develop a yellow tarnish. Associated Minerals include quartz , barite , wittichenite , chalcopyrite and skutterudite . Best Field Indicators are crystal habit, cleavage, softness, color and density.