mineral
Limonite
FeO(OH)·nH2O
AI-generated identification · may be incorrectHardness: 4-5.5 on the Mohs scale; Color: Yellow-brown, dark brown, to nearly black; Luster: Earthy, submetallic, or silky; Crystal structure: Amorphous, typically forms in compact, mammillary, or botryoidal masses; Cleavage: None; Specific gravity: 2.7-4.3
- Hardness
- 4-5
- Color
- Yellow-brown, dark brown, to nearly black
- Luster
- Earthy, submetallic, or silky
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Physical properties
Hardness: 4-5.5 on the Mohs scale; Color: Yellow-brown, dark brown, to nearly black; Luster: Earthy, submetallic, or silky; Crystal structure: Amorphous, typically forms in compact, mammillary, or botryoidal masses; Cleavage: None; Specific gravity: 2.7-4.3
Formation & geological history
Formed through the weathering and oxidation of iron-bearing minerals (like pyrite, magnetite, and hematite) in aqueous or sedimentary environments, often found in gossans and bog iron deposits.
Uses & applications
Historically used as a pigment (ochre), a minor ore of iron, and sometimes polished for ornamental items or lapidary display by collectors.
Geological facts
Limonite is not a single distinct mineral, but rather a mixture of hydrated iron oxide-hydroxides, most commonly goethite, lepidocrocite, and jarosite.
Field identification & locations
Easily identified by its characteristic yellowish-brown to brownish streak and earthy luster. Found worldwide, particularly in weathered iron deposits and soil crusts.
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Other mineral specimens
Gneiss or Schist
Gneiss or Mica Schist with Garnet
Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Granite
Granite (Phaneritic intrusive igneous rock)
igneous
Septarian Pebble
Septarian nodule / Concretion
sedimentary