Pyrite, also known as sulphur pyrite, iron pyrite, fool's gold or fool's gold, is a very common mineral from the class of "sulphides and sulphosalts". Chemically speaking, it is the cubic modification of iron disulphide with the chemical composition FeS2, i.e. it consists of iron and sulphur in a ratio of 1:2.
Pyrite is opaque in any form and predominantly develops idiomorphic crystals in the form of cubes or pentagon dodecahedrons. Octahedrons and disdodecahedrons are also common, as are combinations between these forms. The crystal faces often show a characteristic striation and a lively metallic luster when fresh.
With a Mohs hardness of 6 to 6.5, pyrite is a hard mineral which, like the reference mineral orthoclase, can just about be scored with a steel file.
The name pyrite comes from the Greek πυρ pyr for fire or πυρίτης pyrítes for "flint". A hard flint can be used to chop off chips of pyrite, which ignite and burn:
This property was already used in the Stone Age to light fires.
Pyrite usually occurs in coarse, granular masses or forms spherical to raspberry-shaped, concentric-shell aggregates. Disk-shaped, radially radiating aggregates (pyrite suns) form sedimentary.