mineral

Pyrite (Fool's Gold)

Iron Sulfide (FeS2)

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

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

Identified March 18, 2026More mineral →

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Physical properties

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

Formation & geological history

Formed in high and low-temperature hydrothermal veins, as an accessory mineral in igneous rocks, in metamorphic rocks, and in sedimentary rocks (shale, coal, and limestone) under anaerobic conditions.

Uses & applications

Major source of sulfur for sulfuric acid production; used in the jewelry industry (formerly as 'marcasite'); used as a semiconductor in early radio receivers; popular specimen for mineral collectors.

Geological facts

Known as 'Fool's Gold' because its color and weight can confuse it with real gold. Unlike real gold, which is soft and malleable, pyrite is brittle and will shatter if struck. It creates sparks when struck against steel, which is why it was used in early firearms like the wheel-lock.

Field identification & locations

Identify in the field by checking for cubic crystal structures, brassy luster, and a greenish-black streak when rubbed on a porcelain plate. Common locations include Peru, Spain, Italy, and various mines across the United States. Brittle nature distinguishes it from gold.