CaSO42H2Osta

CaSO42H2Osta appears to be a concatenation or misspelling of the standard chemical notation for calcium sulfate dihydrate. The correct formula is CaSO4·2H2O, representing gypsum, a widely occurring mineral and industrial material.

Calcium sulfate dihydrate, or gypsum, forms from the hydration of anhydrite (CaSO4) and is a member of the monoclinic crystal system. Natural gypsum is typically white or colorless, but impurities can give it gray, yellow, or reddish hues. It has a Mohs hardness of about 2 and a specific gravity near 2.3. Gypsum is moderately soluble in water, with solubility increasing at higher temperatures.

Gypsum forms in evaporite environments, such as saline lakes and seabed evaporations, or by the diagenetic alteration of anhydrite. It commonly occurs in association with other evaporite minerals like halite. The mineral can also crystallize as transparent to translucent crystals or as fibrous or massive masses. In nature, gypsum can dehydrate to calcium sulfate hemihydrate (CaSO4·0.5H2O) upon heating to around 150°C, a material known as plaster of Paris; further heating yields anhydrite (CaSO4) at higher temperatures.

Industrial and practical uses of gypsum are widespread. It is ground into powder for plaster and plasterboard (drywall), used as a filler in paints and paper, and employed as a cement additive to regulate setting time. It also serves as a source of calcium and sulfur in agricultural fertilizers and soil amendments. Varieties such as alabaster and selenite are valued for ornamental carving and sculpture.

In summary, CaSO4·2H2O (gypsum) is the standard notation and widely used form; CaSO42H2Osta is not a recognized conventional name for the compound.