Reference work entry
The chemical composition of pyrite is FeS 2. It is an important sulphur mineral ore with a sulphur content 53.4%. It belongs to the isometric crystal system, and the crystal form is cubic, pentagonal dodecahedral or octahedral. Crystal twinning is common, and the crystal faces are usually striped. It also appears as clumpy, granular, reniform, stalactitic, botryoidal or nodular aggregates. It is light yellow with greenish black streaks. It has opaque diaphaneity, a metallic lustre, a specific gravity of 5.0, a Mohs hardness of 6–6.5 and conchoidal fractures. It is a common secondary mineral in magmatic, sedimentary and metamorphic rocks. Pyrite is a raw material for refining sulphuric acid. Pyrite crystals are very good ornamental stones (Fig. 36).
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