Some variety of alum.

a name for alum occurring in soft masses greasy to the touch.

an alum-containing mineral occurring as soft crystalline deposits on rock; esp. = alunogen, n.

(a) Chemistry a double sulphate of potassium and manganese; (b) Mineralogy = apjohnite, n.

A name for ammonia alum (see alum, n.1 2), esp. as occurring native in brown coal at Tschermig.

Hydrous sulphate of aluminium and sodium; a sodium alum.