Celsian

a mineral; a barium feldspar, with the composition Ba[Al₂Si₂O₈]. The mineral is named in honor of the Swedish scientist A. Celsius. Celsian contains admixtures of K, Ca, and Sr. It crystallizes in the monoclinic system. Its structure, ordering, and conditions of formation are the same as those of other potassium-sodium feldspars. Celsian, which is colorless, has a density of 3,300–3,400 kg/m³ and a hardness of 6–6.5 on Mohs’ scale. A rare mineral, it is usually found in contact metasomatic deposits enriched by manganese rocks. In the USSR it is found in the Ukraine. There are also deposits in Sweden, Japan, and other countries.