1. a mineral consisting of hydrated potassium aluminum sulfate, used historically as a source of alum and in dyeing and tanning
Usage: geology; mineralogy; also called alunite

Examples

• Alumstone deposits were mined in medieval Europe for the production of alum.
• The geologist identified alumstone in the rock sample by its characteristic crystal structure.
• Alumstone served as an important industrial mineral before synthetic alum became widely available.
• The region's alumstone reserves made it a center for textile processing in the 18th century.