mineral

Pyrite in Shale

Iron Sulfide (FeS2)

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

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

Identified April 6, 2026More mineral →

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Physical properties

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

Formation & geological history

Formed in sedimentary rock (shale) under reducing (oxygen-poor) conditions through the action of sulfate-reducing bacteria. Often found in hydrothermal veins and metamorphic rocks as well.

Uses & applications

Historically used as a source of sulfur and sulfuric acid. Today, it is primarily used as a collector specimen, in jewelry (known as marcasite), and occasionally in battery technology studies.

Geological facts

Often called Fool's Gold because its color and metallic luster allow it to be mistaken for gold. However, pyrite is much harder and leaves a greenish-black streak, whereas gold is soft and leaves a yellow streak.

Field identification & locations

Identify in the field by its brittle nature (it shatters instead of flattens like gold), its cubic crystal habits, and the 'sulfur' smell it produces when struck. Frequently found in carbonaceous shales worldwide.