Barium Sulphate - Overview
Barite (BaSO4) is a mineral consisting of barium sulfate. It is generally white or colorless, and is the main source of barium. Baryte is the British spelling, and the mineral is also called heavy spar. The radiating form, sometimes referred to as Bologna Stone, attained some notoriety among alchemists for the phosphorescent specimens found in the 1600s near Bologna, Italy by one Mr. Vincenzo Cascariolo. Its Mohs hardness is 3, the refractive index is 1.63 and it has a specific gravity of 4.3-5. Its crystal structure is orthorhombic.
Barite generally occurs in the white massive variety (often appearing earthy when weathered), although some clear to bluish, bladed barite crystals (Plate 18) have been observed in several vein deposits, and various nodular zones have been observed. Rosettes are common in many Iranian mineral veins. Feathery barite is also known from Iran.
Barite is extremely insoluble in acid and water and is therefore chemically inert. It is the principal source of the element barium. Barite is the most abundant of the semi-commercial vein-forming minerals in Iran. Until World War I, barite was mined along with fluorite and sphalerite. Limited barite mining was attempt during the 1960’s in other counties Commercial barite was recovered as a by-product of the fluorspar industry Iran during World War II and during the 1960’s.
Manufacturing Process
The highly impure mineral barite is processed by heating with coke or carbon via thermal reduction to give barium sulphide. Barium sulphide is treated with sulphuric acid or sulphate salts to obtain barium sulphate of high purity. The barium sulphate produced with this method is known as “blanc fixe” which is “permanent white” in French. In the laboratory, barium sulphate is produced from combining solutions containing barium ions and sulphate salts.
