Roselite is a rare arsenate mineral with chemical formula: Ca2(Co,Mg)[AsO4]2·H2O. It was first described in 1825 for an occurrence in the Rappold mines of Schneeberg, Saxony, Germany and named by Armand Lévy after German mineralogist Gustav Rose. It occurs in cobalt bearing hydrothermal environments and was associated with veins of quartz and chalcedony in the type locality. It has also been reported from Italy, Morocco, Chile, British Columbia and several locations in Germany.