This large cabinet specimen of arsenopyrite was discovered in the polymetallic deposits of Panasquiera Mine, Castelo Branco District, Portugal. The striking iridescence to the crystals in this pocket is uncommon, as this iron arsenic sulfide typically presents as silver-toned with hints of silver-white and dark gray.
Dr. Rob Lavinsky, the owner of The Arkenstone Gallery of Fine Minerals, who acquired this mineral specimen, reports seeing the same iridescence effect, although very rarely, in specimens extracted from mines in China. Arsenopyrite is the most common mineral to contain arsenic and, as such, it emits an odor similar to garlic when heated.
The Arkenstone Gallery of Fine Minerals, www.irocks.com