Wiklundite

Wiklundite is a rare and complex arsenate arsenite-silicate mineral with the chemical formula Pb2(Mn(2+),Zn)3(Fe(3+),Mn(2+))2(Mn(2+),Mg)19(As(3+)O3)2(Si,As(5+)O4)6(OH)18Cl6. The mineral characterizes in a large c unit cell parameter. It was found in Långban, Sweden - a home for many rare and exotic minerals.

Relation to other minerals
Structure of wiklundite is unique. A slightly chemically similar mineral, although lacking manganese and iron, is hereroite.