mineral

Goethite pseudomorph after Pyrite

Goethite (FeO(OH)) pseudomorph after Pyrite (FeS2)

AI-generated identification · may be incorrect

Form: Cuboidal or pyritohedral crystal habit. Hardness: 5-5.5 (Goethite) vs original Pyrite. Color: Dark brown to blackish. Luster: Dull to sub-metallic. Crystal Structure: Orthorhombic. Specific Gravity: 3.3-4.3.

Hardness: 5-5
Color: Dark brown to blackish
Luster: Dull to sub-metallic

Identified June 14, 2026More mineral →

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Physical properties

Formation & geological history

This specimen is a pseudomorph, where the mineral Goethite has replaced the original Pyrite crystal structure through chemical weathering and oxidation while maintaining the original crystal shape. Often found in sedimentary or metamorphic host rocks.

Uses & applications

Primarily for mineral collecting and educational purposes. Historically, Goethite is an ore of iron.

Geological facts

These are often nicknamed 'Prophecy Stones' in a metaphysical context or 'Limonite/Goethite cubes' in geology. The term pseudomorph literally means 'false form'.

Field identification & locations

Identify by the distinct cubic or multi-faceted pyritohedral shape combined with a dark brown, rusty oxidation color and lack of metallic brassy luster characteristic of fresh pyrite. Commonly found in desert environments or weathering outcrops.