Xanthiosite is a nickel arsenate mineral. It was first discovered in Germany in 1858 and named by Gilbert Joseph Adam in 1869. Deposits The type locality of Xanthiosite is Johanngeorgenstadt, it may also be found in Greece. Categories: Arsenate Minerals, Nickel Minerals, Monoclinic Minerals, Minerals In Space Group 14, Minerals Described In 1858