Pyrite

Physical Properties

Hardness: 6-6.5 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.

Formation & Geological History

Formed in high and low temperature hydrothermal veins, as an accessory mineral in igneous rocks, in contact metamorphic rocks, and in sedimentary rocks such as shale and coal. It forms in oxygen-poor environments.

Uses & Applications

Historically a source of sulfur and sulfuric acid. Today used in jewelry (marketed as 'marcasite'), as a grit in grinding wheels, and as a popular specimen for mineral collectors.

Geological Facts

Known as 'Fool's Gold' because its color and metallic luster frequently lead novice prospectors to mistake it for real gold. Some pyrite specimens have been found to contain small amounts of actual gold as inclusions.

Field Identification & Locations

Identify by its brittle nature (it crushes to black powder, whereas gold is malleable) and its greenish-black streak when rubbed on a porcelain plate. Common worldwide, notably in Spain, Italy, and the USA.

Identified on: 5/14/2026

Mode: Standard