mineral

Pyrite (Fool's Gold)

Iron Sulfide (FeS2)

Hardness: 6-6.5 on Mohs scale; Color: Pale brass-yellow to golden; Luster: Metallic; Crystal Structure: Isometric (often cubic or pyritohedral); Cleavage: Indistinct; Specific Gravity: 4.8–5.0; Streak: Greenish-black to brownish-black.

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

Identified March 15, 2026More mineral →

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Physical properties

Formation & geological history

Formed in a variety of geological settings including hydrothermal veins, as an accessory mineral in igneous rocks, in contact metamorphic rocks, and in sedimentary rocks like shale and coal. Formation spans all geological ages.

Uses & applications

Historically used as a source of sulfur and sulfuric acid. Today, it is used in the production of paper, fertilizers, and occasionally as a semiconductor. It is popularized in jewelry (as marcasite) and is a very common collector mineral.

Geological facts

Known as 'Fool's Gold' because its color often confused inexperienced prospectors with actual gold. During the 16th and 17th centuries, it was used as a source of ignition in early firearms (wheel-locks). Unlike gold, it is brittle and will shatter if struck, and it produces a black streak rather than a yellow one.

Field identification & locations

Identify in the field by its cubic crystal habit, brassy color, and high hardness (it can scratch glass). It is commonly found globally, with notable deposits in Spain, Peru, Italy, and the USA. For collectors, cubic and sun-disk forms are highly prized.