cobaltite (cobalt glance) Mineral, CoAsS; sp. gr. 6.0–6.5; hardness 5–6; cubic; from white to dark grey or greyish-black, all with a reddish tinge; grey–black streak; metallic lustre; crystals octahedra, cubes, and pentagonal-dodecahedra, also occurs massive, and in irregular grains; cleavage perfect cubic; occurs mainly in hydrothermal veins and contact metamorphic zones, and is associated with chalcopyrite, sphalerite, chlorite, tourmaline, and apatite. It is one of the principal ore minerals for cobalt.

cobalt (symbol Co) Metallic element, a transition metal, discovered c.1735. It is found in cobaltite and smaltite, but mostly obtained as a by-product during the processing of other ores. Cobalt is a constituent of vitamin B¹². It is used in high-temperature steel, artists' colours (cobalt blue), jet engine manufacture, cutting tools and magnets. Cobalt-60 (half-life 5.26yr) is an artificial isotope used as a source of gamma rays in radiotherapy and tracer studies. Properties: at.no. 27; r.a.m. 58.9332; r.d. 8.9; m.p. 1495°C (2723°F); b.p. 2870°C (5198°F); most common isotope Co⁵⁹ (100%).