Pyrite, also known as "Fool's Gold," is a common iron sulfide mineral known for its brass yellow colour and metallic lustre which can cause it to be mistaken as gold. However, hardness, streak, specific gravity, and habit are diagnostic properties that differentiate pyrite from gold. Pyrite often occurs in cubic to octahedron forms with striated cleavage faces, as seen here, with a specific gravity of 4.9-5.2 and produces a dark greenish-black streak. In contrast, gold occurs as flakes or shapeless nuggets and sheets with a much heavier specific gravity of 19.3 in its pure form, while producing a golden/yellow streak matching its colour. Gold is also a very malleable and ductile metal with a hardness of 2.5-3 and pyrite is more brittle with a hardness of 6-6.5. Pyrite occurs in several environments: igneous, sedimentary, and metamorphic rocks, as well as hydrothermal vents. The mineral was once an ore of sulfur and sulfuric acid and used as a fire starter. Now mainly used as a gemstone or regarded as an ore indicator as it is associated with important sulfide minerals and metal ores, such as chalcopyrite and gold.