Chrysocolla is a secondary copper mineral with a blue-green color, that some people mistake for turquoise. The main difference is turquoise contains phosphorus and chrysocolla does not. Chrysocolla often contains other copper seconaries, such as malachite, tenorite or cuprite. Chrysocolla is often opalized and tends to fracture or can be soft and chalky in places. Therefore, chrysocolla is often stabilized to make it solid and hard enough to take a good polish. It generally takes a good polish with tin oxide or diamond, followed with green rouge (Zam is a brand name for green rouge). Mohs hardness 2.5 to 5.0.