Limonite/Goethite pseudomorph after Pyrite
Goethite (FeO(OH)) with Hematite inclusions · Mineral Specimen / Collector Mineral
Crystal System
Orthorhombic; appearing in Cubic habits (pseudomorphous after pyrite)
Mineral Group
Oxides / Hydroxides
Chemical Formula
FeO(OH)·nH2O
Formation Process
Secondary formation via oxidation and hydration of iron-rich sulfide minerals (pyrite or marcasite) in oxidizing environments
About This Crystal
An opaque, earthy to sub-metallic brown or yellowish-brown mineral. This specimen shows a rough, weathered texture with remnants of a cubic or pyritohedral shape, typical of pseudomorphism.
Physical Characteristics
Color: Dark brown to ochre; Streak: Yellow-brown; Fracture: Uneven/Conchoidal; Luster: Dull to sub-adamantine; Specific Gravity: 2.7–4.3
Optical Properties
Opaque; No significant birefringence or pleochroism visible in massive/weathered forms
Hardness & Durability
Origin Region
Global; notable specimens from Morocco (White Desert), USA (Arizona, Colorado), and Spain
Hardness & Durability
Mohs Hardness: 4.0 – 5.5; Brittle; variable durability due to porous or weathered structure
Care & Maintenance
Avoid acidic cleaners; clean with a soft dry brush; store in a dry environment to prevent further hydration or crumbly decay
Rarity & Value
Common mineralogically, but well-defined 'Prophecy Stone' or 'Iron Cross' pseudomorphs are valued by collectors ($5 - $50 depending on size/form)
Special Characteristics
Pseudomorphism: the mineral has replaced the internal chemistry of pyrite while retaining its original external crystal shape (cubic)
Lore & History
Historically used as an iron ore and brown pigment (ochre). In metaphysical circles, often called 'Prophecy Stones' and associated with grounding and visionary work.