Baryte, or barite, (BaSO4) is a mineral consisting of barium sulfate. The baryte group consists of baryte, celestine, anglesite and anhydrite. Baryte itself is generally white or colorless, and is the main source of barium. Baryte and celestine form a solid solution (Ba,Sr)SO4. The radiating form, sometimes referred to as Bologna Stone, attained some notoriety among alchemists for the phosphorescent specimens found in the 17th century near Bologna by Vincenzo Casciarolo. The American Petroleum Institute specification API 13/ISO 13500 which governs baryte for drilling purposes does not refer to any specific mineral, but rather a material that meets that specification. In practice this is usually the mineral baryte. The term ''primary baryte'' refers to the first marketable product, which...'
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