Barite: Gemstone Information
Barite is barium sulphate (BaSO4) at one time known among miners as heavy spar. Fine and often well-formed transparent to opaque orthorhombic crystals (more than 70 forms are recorded) are most commonly white though yellow, green, red, blue or brown colours are sometimes found. The massive white material may resemble marble.The hardness is 3 and the SG 4.3–4.6; for gemmy material the values are near 4.47; the RIs are 1.636, 1.637 and 1.648, DR 0.012 biaxial positive.The crystals show two directions of perfect cleavage. Barite sometimes fluoresces and often phosphoresces with a faint blue or light green colour under UV. Barite has a worldwide occurrence, gemmy material comes from Colorado and Sardinia. Beautiful blue crystals from the Sterling area of Colorado could be faceted but such crystals should be left alone. Fine yellow material with clear areas, from Cumbria, England, tends to be more massive and faceting could be appropriate here. A brown stalagmitic variety when sectioned shows a concentric structure. Barite is the most common barium mineral and occurs in low-temperature hydrothermal veins and in residual deposits from weathered barium-bearing limestones. Transparent orange barite is found at the Rosh Pinah mine, Namibia, and a deposit in Nevada, USA, has produced yellow specimens.