mineral

Pyrite (on a metal substrate)

Iron Sulfide (FeS2)

Hardness: 6-6.5 Mohs scale. Color: Pale brass-yellow to brass-yellow. Luster: Metallic. Crystal structure: Isometric (often cubic or pyritohedral). Cleavage: Indistinct. Specific gravity: 4.9–5.2.

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

Identified March 15, 2026More mineral →

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Physical properties

Hardness: 6-6.5 Mohs scale. Color: Pale brass-yellow to brass-yellow. Luster: Metallic. Crystal structure: Isometric (often cubic or pyritohedral). Cleavage: Indistinct. Specific gravity: 4.9–5.2.

Formation & geological history

Formed in high and low-temperature hydrothermal veins, by magmatic segregation, and as an accessory mineral in igneous rocks, as well as in sedimentary rocks (shales, coal) and metamorphic rocks. It can form in any geological age from the Archean to the Holocene.

Uses & applications

Primary source of sulfur and sulfuric acid used in industry. Historically used as a spark source for wheel-lock firearms. Used in jewelry (marketed as 'Marcasite') and as a popular collector mineral.

Geological facts

Commonly known as 'Fool's Gold' due to its deceptive color. It is the most common sulfide mineral. Under certain conditions, it can oxidize and cause 'pyrite rot' which destroys museum specimens. It can sometimes contain trace amounts of actual gold.

Field identification & locations

Identify in the field by its brassy color, cubic crystal habit, and greenish-black streak (real gold has a yellow streak). It is found worldwide, with notable deposits in Spain, Peru, Italy, and the USA. Collectors look for sharp, mirror-finish cubic facets.