Absolutely stunning color makes this unusually large matrix krohnkite a beauty to look at, but its also a super rich example of an extremely rare copper species. Chuqui is located 15 km N of Calama, II Region, Chile. It is the world's largest open pit copper mine, according to MinDat. It hit its heyday by the mid-1900s and during that time produced innumerable mineral specimens which sadly went to the crusher. However, a few people there saved some pieces, and it later turned out that the mine produced a host of new species (many mislabeled in these old collections), identified only long after they were taken from the ground. This one was named after B. Krohnke, who first analyzed the mineral and realized that not all "chalcanthite" from this mine was that common stuff! Krohnkite is, instead, a very rare copepr sulfate. Ex Philadelphia Academy of Natural Science.