Pyrite

Pyrite, also known as "Fool's Gold" because of its brassy-yellow metallic colour, is the most common sulphide mineral in rocks of all ages, being found in virtually every geological environment. It is easily distinguishable from gold as it has a lower specific gravity (specific gravity of gold is 15.9-19.3) and it is harder (hardness of gold is 2.5-3).

Pyrite is a common component of sedimentary rocks and metamorphosed sediments, is an accessory mineral in many igneous rocks, and forms large bodies in hydrothermal deposits.

Chemical composition - FeS 2 Hardness - 6-6.5 Specific gravity - 4.9-5.2 Transparency - Opaque Colour - Brassy yellow Streak - Greenish black Lustre - Metallic Cleavage/fracture - Non-existent / hackly, conchoidal Crystal habit/mode of occurrence - Prismatic (cube, octahedron and pyritohedron [a dodecahedron with pentagonal faces]) / massive, granular.