mineral

Pyrite (Fool's Gold)

Iron Sulfide (FeS2)

Hardness: 6-6.5 Mohs. Color: Pale brass-yellow. Luster: Metallic. Crystal structure: Isometric. Cleavage: Indistinct. Specific gravity: 4.8-5.0.

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

Identified April 6, 2026More mineral →

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Physical properties

Hardness: 6-6.5 Mohs. Color: Pale brass-yellow. Luster: Metallic. Crystal structure: Isometric. Cleavage: Indistinct. Specific gravity: 4.8-5.0.

Formation & geological history

Formed in high and low-temperature hydrothermal veins, by magmatic segregation, and as an accessory mineral in igneous, metamorphic, and sedimentary rocks. Common in coal beds and as a replacement mineral in fossils.

Uses & applications

Historically used as a source of sulfur and in the production of sulfuric acid. Occasionally used as a gemstone (referred to as marcasite in jewelry) or in radio receivers. Primarily a collector's mineral.

Geological facts

Known as 'Fool's Gold' because it is often mistaken for real gold, though it is much harder and more brittle. It can create sparks when struck against steel, which made it useful in prehistoric and early firearm fire-starting.

Field identification & locations

Identify by its brittle nature (it crushes to powder, gold flattens), its greenish-black streak (gold has a yellow streak), and its hardness (it can scratch glass, gold cannot). Found worldwide, especially in Spain, Italy, and the USA.