Limonite
Rock made of goethite, lepidocrocite
Common · FeO(OH)·nH₂O
Not a mineral but a field name for rusty brown masses of hydrated iron oxides, chiefly goethite with lepidocrocite, which only X-ray diffraction tells apart. Its yellowish brown streak sets it apart from hematite and magnetite. Bog iron ore and limonite mudstones have been smelted for iron since at least 400 BC, Cyprus was famous for its yellow ochre, roasted limonite gave red ochres and umbers, and nickel-rich limonite laterites now hold the largest reserves of nickel.
Rock
- Kind of rock
- Chemical sedimentary rock
- Rock family
- Sandstone, shale and clay
- Deposits
- Lateritic deposit, Bog iron, Ironstone beds, Oxidized zone (gossan)
- Metals
- Iron, Nickel
- How it forms
- Iron carried by groundwater oxidises at the surface, in bogs, in gossans over sulfide ore and in laterites.
- Uses
- Iron ore since the Iron Age.
Identity
- Formula
- FeO(OH)·nH₂O
- Chemical class
- Oxide
- Also known as
- Brown iron ore, Brown hematite, Bog iron ore
- Ore of
- Iron, Nickel
Crystallography
- Crystal system
- Amorphous
- Habits
- Earthy, Massive, Botryoidal, Stalactitic, Nodular
- Fracture
- Uneven
Physical properties
- Mohs hardness
- 4
- Density
- 3.6 g/cm³
- Luster
- Earthy, Dull
- Colors
- yellowish brown, brown, dark brown, ocher yellow
- Streak
- yellowish brown
- Transparency
- Opaque
Geology
- Origins
- Sedimentary
- Host rocks
- Sandstone, shale and clay
- Associated minerals
- Goethite, Hematite, Magnetite, Siderite, Pyrite
- Geography
- worldwide, Cyprus
Classification
- Rarity
- Common
- Gem quality
- No
Sources
- Limonite. Wikipedia.
- Bog iron. Wikipedia.
- C. R. Hallsworth, R. W. O’B. Knox, BGS Rock Classification Scheme, Volume 3: Classification of sediments and sedimentary rocks (Research Report RR 99-03). British Geological Survey, 1999.
- Limonite: Mineral information, data and localities. mindat.org.
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