mineral

Pyrite (Fool's Gold)

Iron Sulfide (FeS2)

Hardness: 6-6.5 Mohs scale; Color: Pale brass-yellow to golden yellow; Luster: Metallic; Crystal Structure: Isometric/Cubic; Cleavage: Indistinct; Specific Gravity: 4.8–5.0.

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

Identified March 22, 2026More mineral →

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Physical properties

Hardness: 6-6.5 Mohs scale; Color: Pale brass-yellow to golden yellow; Luster: Metallic; Crystal Structure: Isometric/Cubic; Cleavage: Indistinct; Specific Gravity: 4.8–5.0.

Formation & geological history

Forms in a variety of geological settings, including hydrothermal veins, as an accessory mineral in igneous rocks, and by precipitation in sedimentary environments. It is found in rocks of all geological ages, from Precambrian to the present.

Uses & applications

Historically used as a source of sulfur and sulfuric acid. Today, it is primarily used as a minor ore of iron, in the production of lithium batteries, and extensively in jewelry (often marketed as 'marcasite') and as a popular specimen for collectors.

Geological facts

Known as 'Fool's Gold' because its color and metallic luster often misled amateur prospectors during the Gold Rush. Unlike gold, pyrite is brittle and leaves a greenish-black streak on porcelain, whereas gold is malleable and leaves a yellow streak.

Field identification & locations

Identify in the field by its brassy color, cubic crystal habit, and high hardness (it can scratch glass). It is commonly found in Peru, Spain, Italy, and the USA. Collectors should keep specimens dry, as humidity can cause 'pyrite disease' (oxidation into iron sulfates).