Alum
Alum found at archaeological sites

The western desert of Egypt was a major source of alum substitutes in antiquity. These evaporites were mainly FeAl (SO) ·22 H O, MgAl (SO) ·22 H O, NaAl(SO) ·6 H O, MgSO ·7H O and Al (SO) ·17 H O. The Ancient Greek Herodotus mentions Egyptian alum as a valuable commodity in The Histories.

The production of potassium alum from alunite is archaeologically attested on the island Lesbos. The site was abandoned during the 7th century CE, but dates back at least to the 2nd century CE. Native alumen from the island of Melos appears to have been a mixture mainly of alunogen (Al (SO) ·17 H O) with potassium alum and other minor sulfates.
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