Gypsum is a soft mineral ground up to make plaster. Mined gypsum, gypsum board, a gypsum quarry.
Heating it drives off water and leaves plaster of Paris, which sets when water is added back — that reversible reaction is the whole basis of plastering and of plasterboard. It is soft enough to scratch with a fingernail, which makes it the standard for hardness two on the Mohs scale. Alabaster is a fine-grained form of gypsum used for carving.
1noungypsumA soft mineral ground up to make plaster.
“The builders used plasterboard made from gypsum for the new walls.”
gypsum is a mineral.
Latin gypsum comes from Greek gypsos, chalk or plaster, itself probably from a Semitic source. Gesso, the painter's ground, is the same word through Italian.
Ancient Greek
γύψος
Latin
gypsum
English, today
gypsum
From Latin gypsum, from Ancient Greek γύψος. a doublet of gesso.
Etymology from Wiktionary, CC BY-SA