Diamond cutters used it to separate diamonds from metalline powders. It was also used in etching copper or brass plates. It was mixed
Kaynak: Aqua fortis

no part of the Minerall stone (Quatenus a stone, fermented with metalline and earthy nature) .. .marveously subtile... Angellicall stone
Kaynak: Angelicall Stone

though alloys of it with other metalline substances have been procured sufficiently distinct to indicate the probable nature of alumina
Kaynak: Aluminium