Definify.com
Webster 1913 Edition
Gypsum
Gyp′sum
(jĭp′sŭm)
, Noun.
[L.
gypsum
, Gr. γύψος
; cf. Ar. jibs
plaster, mortar, Per. jabsīn
lime.] (Min.)
A mineral consisting of the hydrous sulphate of lime (calcium). When calcined, it forms plaster of Paris.
Selenite
is a transparent, crystalline variety; alabaster
, a fine, white, massive variety.