a white, grey, or reddish mineral consisting of hydrated aluminium sulphate. It occurs in volcanic igneous rocks and is a source of potassium and aluminium compounds. Formula: KAl3(SO4)2(OH)6
Word origin
C19: from French alun alum (from Latin alūmen) + -ite1
alunite in American English
(ˈæljuˌnaɪt; ˈæljəˌnaɪt)
noun
a semihard, hydrous mineral, KAl3(SO4)2(OH)6, used to produce alum