Niccolite, also called kupfernickel, is a coppery-red ore of nickel with an easily tarnished metallic luster. It consists of nickel arsenide (NiAs) and is often found in veins with some cobalt, iron, and sulfur, notably pyrrhotite. It crystallizes in the hexagonal system generally in columnar masses, rarely as tabular crystals. Hardness: 5–5.5; relative density 7.8.