Hisingerite

Hisingerite is an iron(III) mineral with formula Fe 5(OH. A black or dark brown, lustrous secondary mineral, it is formed by the weathering or hydrothermal alteration of other iron silicate

It was first described in 1828 for an occurrence in Riddarhyttan, Vastmanland. It was named after Wilhelm Hisinger

There are also aluminian hisingerite variety in which one of the iron atoms is replaced by aluminium and chrome-alumina-hisingerite variety in which chromium