mineral

Pyrite (Pseudomorph)

Iron Sulfide (FeS2)

Hardness: 6-6.5; Color: Brass-yellow to dark gray/black (if tarnished or oxidized); Luster: Metallic; Crystal Structure: Isometric (Cubic); Cleavage: Indistinct; Specific Gravity: 4.9-5.2

Hardness: 6-6
Color: Brass-yellow to dark gray/black (if tarnished or oxidized)
Luster: Metallic

Identified June 22, 2026More mineral →

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Physical properties

Hardness: 6-6.5; Color: Brass-yellow to dark gray/black (if tarnished or oxidized); Luster: Metallic; Crystal Structure: Isometric (Cubic); Cleavage: Indistinct; Specific Gravity: 4.9-5.2

Formation & geological history

Formed in sedimentary rocks through hydrothermal activity or as a replacement mineral in organic-rich shales. These cubic shapes often form in oxygen-poor environments. This specimen appears to be a natural cubic crystal.

Uses & applications

Major source of sulfuric acid and sulfur; historically used to create sparks for firearms (wheel-locks); popular among collectors and used in costume jewelry (marcasite jewelry).

Geological facts

Commonly known as Fool's Gold due to its resemblance to precious metals. Pyrite can actually contain small amounts of real gold. The term pseudomorph refers to pyrite that has been chemically replaced by goethite or limonite while retaining its original cubic shape.

Field identification & locations

Identified by its perfect cubic habit and high density. Found globally, with notable deposits in Spain, Italy, and the USA. Collectors look for sharp, mirror-finish faces.