Arsenopyrite with quartz; specimen from China. Image source: Wright's Rock Shop, Hot Springs, Arizona.
Arsenopyrite, also known as mispickle, is a silvery-white mineral with metallic luster, crystallizing in the monoclinic system. Arsenopyrite is iron sulfarsenide (FeAsS). It is the chief ore of arsenic, and is found, among other places, in the United States, Canada, Germany, England, and Scandinavia.