stannite Comparatively rare mineral, Cu2FeSnS4; sp. gr. 4.3–4.5; hardness 3–4; tetragonal; steel-grey with an olive-green tinge on fresh surfaces, which become yellowish on exposure; black streak; metallic lustre; crystals rare, cubes or tetrahedra, but normally the grains are irregular or massive; occurs in hydrothermal tin-ore deposits and in association with cassiterite, chalcopyrite, and wolframite, also in stanniferous sphalerite–galena ores, and associated with sphalerite, pyrrhotite, and galena.
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