mineral

Pyrite

Iron Sulfide (FeS2)

Hardness: 6-6.5 on Mohs scale; Color: Pale brass-yellow; Luster: Metallic; Crystal Structure: Isometric (cubes, pyritohedrons); Cleavage: Indistinct; Specific Gravity: 4.9-5.2

Hardness: 6-6
Color: Pale brass-yellow
Luster: Metallic

Identified June 30, 2026More mineral →

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Physical properties

Hardness: 6-6.5 on Mohs scale; Color: Pale brass-yellow; Luster: Metallic; Crystal Structure: Isometric (cubes, pyritohedrons); Cleavage: Indistinct; Specific Gravity: 4.9-5.2

Formation & geological history

Forms in diverse environments including hydrothermal veins, as an accessory mineral in igneous rocks, in contact metamorphic rocks, and in sedimentary rocks like shale and coal. Formation occurs through the reaction of iron-rich fluids with sulfur.

Uses & applications

Used historically as a source of sulfur and sulfuric acid. Today it is used in the manufacture of paper, fertilizers, and batteries. It is also a popular collector's mineral and is sometimes used in jewelry under the name 'marcasite'.

Geological facts

Commonly known as 'Fool's Gold' because its color and metallic luster often led prospectors to mistake it for the real thing. It can actually contain small amounts of actual gold hidden within the crystal structure. It produces sparks when struck against steel.

Field identification & locations

Identify in the field by its brassy color, greenish-black streak (real gold has a yellow streak), and cubic habit. Found globally with famous deposits in Spain, Peru, Italy, and the USA. It is much harder than gold and cannot be scratched by a fingernail.