Roselite

This sample of roselite is displayed in the Smithsonian Museum of Natural History. Roselite is an arsenate mineral which contains arsenic, calcium, cobalt and magnesium. It has the composition Ca₂(Co,Mg)(AsO₄)₂.2H₂O. This sample is about 6x8 cm and is from Arhbar mine, Bou Azzer, Morocco.