mineral

Pyrite (on Quartz matrix)

Iron Sulfide (FeS2)

Hardness: 6-6.5 (Mohs); Color: Brass-yellow, pale gold; Luster: Metallic; Crystal Structure: Isometric (often cubic or pyritohedral); Cleavage: Indistinct; Specific Gravity: 4.8-5.0

Hardness: 6-6
Color: Brass-yellow, pale gold
Luster: Metallic

Identified March 29, 2026More mineral →

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Physical properties

Hardness: 6-6.5 (Mohs); Color: Brass-yellow, pale gold; Luster: Metallic; Crystal Structure: Isometric (often cubic or pyritohedral); Cleavage: Indistinct; Specific Gravity: 4.8-5.0

Formation & geological history

Formed through hydrothermal precipitation in veins, sedimentary deposits in anaerobic conditions, and as an accessory mineral in igneous rocks. It can form in almost any geological age where sulfur and iron are present.

Uses & applications

Used industrially for the production of sulfur dioxide (sulfuric acid production), as a semiconductor in early radio receivers, and widely used in jewelry (marketed as 'marcasite') and as a popular collector's mineral.

Geological facts

Commonly known as 'Fool\'s Gold' because its color and metallic luster frequently deceived prospectors. Unlike gold, pyrite is brittle and cannot be scratched by a copper penny. It is also known to create sparks when struck against steel.

Field identification & locations

Identify in the field by its brassy color, greenish-black streak (on a porcelain plate), and cubic crystal habit. Commonly found in Navajún (Spain), Peru, and across the United States. Ensure it is stored in dry conditions as it can oxidize ('pyrite disease') in high humidity.