sphalerite (black jack, zinc blende) Mineral, ZnS; sp. gr. 3.9–4.1; hardness 3.5–4.0; cubic; colour variable, but commonly yellow, brown, or black, and crystals can be transparent to translucent; brownish red to bright yellow or white streak; resinous to near-metallic lustre; crystals tetrahedral or dodecahedral, with curved faces, but also granular, fibrous, or botryoidal; conchoidal fracture; cleavage perfect galena; the most common ore mineral for zinc metal, Zn—Pb is common in strata-bound veins and massive sulphide deposits, frequently associated with galena in hydrothermal veins, and in limestones where it occurs by replacement, commonly with pyrite, pyrrhotite, and magnetite; dissolves in concentrated nitric acid with the separation of sulphur.

sphalerite (blende) Sulphide mineral composed of zinc sulphide (ZnS), an important source of zinc. It has cubic system tetrahedral crystals or granular masses. It is white when pure, but more commonly yellow, black, or brown with a resinous lustre. Hardness 3.5–4; r.d. 4.