sedimentary
Limonite (Iron Ore)
Hydrated ferric oxide mixture (FeO(OH)·nH2O)
Hardness: 4.0-5.5 | Color: Brown, yellowish-brown, ochre | Luster: Dull, earthy | Crystal Structure: Amorphous/Microcrystalline | Cleavage: None | Specific Gravity: 2.7-4.3
- Hardness
- 4
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 4.0-5.5 | Color: Brown, yellowish-brown, ochre | Luster: Dull, earthy | Crystal Structure: Amorphous/Microcrystalline | Cleavage: None | Specific Gravity: 2.7-4.3
Formation & geological history
Formed as a secondary mineral through the oxidation and hydration of other iron-bearing minerals (like pyrite or magnetite) in weathered zones of ore deposits or as sedimentary bog iron.
Uses & applications
Historically used as a major ore of iron; currently used predominantly as a natural pigment (yellow ochre) in paints, dyes, and cosmetics.
Geological facts
Limonite is not a true mineral in the strictest sense but a mixture of minerals, primarily goethite. It was the source of iron for many early industrial ironworks.
Field identification & locations
Identify by its yellowish-brown streak on a porcelain plate and lack of magnetism compared to magnetite. Found globally in weathered capping of iron-rich mineral veins (gossans).
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary