Although arsenopyrite is a fairly common mineral, it is frequently found in messy clusters and plates, and usually larger in size. This wonderful thumbnail specimen features a sharp, lustrous, well-formed arsenopyrite crystal, sprinkled with tiny chalcopyrite crystals as a nice accent. A striking specimen at any size! From the thumbnail collection of Martin C. Jensen (b. 1959) of Reno, Nevada, USA. He is not only a mineral collector, but an SEM specialist at the Mackay School of Mines, and has contributed multiple studies on localities in the western United States. The mineral species Jensenite is named in his honor.