updated in 2018
A relatively common mineral, pyrite forms in sedimentary deposits, hydrothermal veins and metamorphic rocks. Pyrite is a one of 350 minerals of the sulfide chemical class that consist of a combination of sulfur and one or more metals.
Pyrite is always a yellow color but it is not always bright and shinny, may tarnish to a dark color or have iridescence.
Crystal forms are often cubic and may be striated on the sides, also frequently octahedral and pyritohedron. Inter-grown crystals are common, may also be found as granular, massive, stalactitic, radiated and globular.
Pyrite has a relatively weak sulfur-sulfur covalent bond which can break down (oxidize) in the presents of water and oxygen. All pyrite specimens are susceptible to this oxidation in varying degrees. When pyrite oxidizes it breaks down in to iron ions and sulfuric acid. Some pyrites decompose rather quickly while others remain stable for many years. It is best to store pyrite specimens in a dry environment and away from other minerals that could be damage by the out gassing of sulfuric acid.
Pyrite's gold coloring has given it the title of fools-gold.
Hardness - 6 - 6.5
Chemical Class - Sulfide
Crystal System - Isometric Diploidal