Carrollite is a Sulphide of Cobalt and Copper, often with substitutions of Nickel. Carrollite like many Sulphides is in the Isometric crystal systen and is largely a silver colored metalloid which rarely associates with a handful of other minerals such as Calcite, Native Elements, and, other Sulphides. Carrollite can also rarely have a surface iridescence.
Carrollite was named for Carroll County, Maryland which is the location of the minerals Type-Locality, Patapsco Mine. While Carrollite is reported from all over the world the finest specimens have come from the Kamoya South II Mine in the Democractic Republic of the Congo.
What to look for: Isolated and Well Formed Crystals, Luster, Less or No Damage, Associations, Iridescence, and, Specimens on Matrix.