Domeykite is a rare copper arsenide first described in 1845 from Chile. This rich old-time specimen from the Philadelphia Academy features a thick vein of lustrous, brassy-bronzy domeykite microcrystals in a quartz-rich matrix. The Sheldon Mine opened in 1853 and is located in Michigan's famous Copper Country. One of the two, old Academy labels states that domeykite is a "New Mineral," indicating that this specimen was probably collected in the 1850s. Hefty for its size (rich in copper) at 219 grams or 7.7 ounces.