Disclosed is an improved alpha-type calcium sulfate hemihydrate. Methods of producing an improved powdered calcium sulfate hemihydrate (CaSO.sub.4.1/2H.sub.2O) [alpha-type] compound are disclosed, at least one method including forming calcium sulfate dihydrate (CaSO.sub.4O.2H.sub.2O) into a briquette, calcining the briquette to transform the calcium sulfate dihydrate to calcium sulfate hemihydrate [alpha-type], drying the calcium sulfate hemihydrate [alpha-type] briquette, and optionally grinding the briquette. Also disclosed are methods of producing an improved gypsum plaster including producing the disclosed powdered calcium sulfate hemihydrate [alpha-type] and mixing the powdered calcium sulfate hemihydrate [alpha-type] with water.