These samples of carrollite are displayed in the Smithsonian Museum of Natural History. Carrollite is a sulfide mineral of copper, cobalt and nickel with the composition Cu(Co,Ni)2S4 . The samples are to the same scale with the left one being about 3x8 cm. They are from Kamboye, Shaba, D. R. Congo. The carrollite is formed with quartz.