Calcium sulfate (or calcium sulphate) is an inorganic salt with the chemical formula CaSO
4. It occurs in several hydrated forms; the anhydrous state (known as anhydrite) is a white crystalline solid often found in evaporite deposits. Its dihydrate form is the mineral gypsum, which may be dehydrated to produce bassanite, the hemihydrate state. Gypsum occurs in nature as crystals (selenite) or fibrous masses (satin spar), typically colorless to white, though impurities can impart other hues. All forms of calcium sulfate are sparingly soluble in water and cause permanent hardness when dissolved therein.
⭐ Core Definition: Calcium sulphate
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Calcium sulphate in the context of Blackboard
A blackboard or a chalkboard is a reusable writing surface on which text or drawings are made with sticks of calcium sulphate or calcium carbonate, better known as chalk.
Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone.