Mineral pseudomorph
Limonite after Pyrite (Prophecy Stone)
Limonite (FeO(OH)·nH2O) replacing Pyrite (FeS2)
Hardness: 4.0-5.5 (Mohs scale), Color: Dark brown to black, Luster: Sub-metallic to dull/earthy, Crystal Structure: Cubic or orthorhombic (inherited from pyrite), Cleavage: None, Specific Gravity: 3.0-4.3
- Hardness
- 4
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Physical properties
Hardness: 4.0-5.5 (Mohs scale), Color: Dark brown to black, Luster: Sub-metallic to dull/earthy, Crystal Structure: Cubic or orthorhombic (inherited from pyrite), Cleavage: None, Specific Gravity: 3.0-4.3
Formation & geological history
Formed through a process called pseudomorphism where original pyrite crystals are chemically replaced by iron oxides (limonite/goethite) over millions of years due to oxidation and hydration in sedimentary environments, specifically the White Desert of Egypt.
Uses & applications
Primarily used as a collector mineral and a 'meditation stone' in metaphysical communities. It has no major industrial or construction uses due to its brittle nature.
Geological facts
This specimen is a 'pseudomorph,' meaning 'false form.' While it looks like an iron-rich crystal, it has completely changed its chemical identity while keeping the shape of the original mineral. The most famous specimens come from the Farafra Oasis in Egypt.
Field identification & locations
Identify in the field by its distinct cubic or star-like 'spiky' shape and its high weight (density) relative to its size. It often leaves a yellow-brown streak on unglazed porcelain. Commonly found in desert regions where pyrite has oxidized.
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