Limonite/Goethite pseudomorph
Goethite-Limonite mixture (alpha-FeO(OH)) · Mineral Specimen / Ore Mineral
Crystal System
Orthorhombic; typically massive, earthy, or botryoidal habit as seen in the grainy and pitted surface.
Mineral Group
Oxides / Hydroxides
Chemical Formula
FeO(OH)·nH2O
Formation Process
Formed through the secondary weathering of iron-rich primary minerals (like pyrite or magnetite) in sedimentary or oxidation zones.
About This Crystal
Opaque, earthy transition mineral showing a mix of ochre-yellow to dark brownish-black. The texture is porous and vuggy with a sub-metallic to dull luster.
Physical Characteristics
Color varies from yellow-brown to black; streak is yellowish-brown. Dense and brittle with uneven, earthy fracture. Non-fluorescent.
Optical Properties
Opaque; sub-metallic luster on fresh surfaces, becoming dull upon weathering. No significant play of color.
Hardness & Durability
Origin Region
Worldwide; commonly from weathered iron deposits in Australia, Germany, and the USA (Appalachians).
Hardness & Durability
Mohs hardness of 4 to 5.5. Brittle and prone to crumbling if exposed to physical shock or acidic environments.
Care & Maintenance
Keep dry as it is porous. Clean with a soft dry brush only; avoid water and ultrasonic cleaners which may cause the specimen to disintegrate.
Rarity & Value
Very common; primarily valued as an iron ore or a geological specimen rather than for jewelry.
Special Characteristics
May form as a pseudomorph, replacing the shape of original crystals like pyrite cubes while retaining its own chemistry.
Lore & History
Historically used as 'Yellow Ochre' pigment by ancient civilizations for cave paintings and pottery dyes.