mineral
Limonite or Ironstone Nodule
Hydrated iron oxide-hydroxide (FeO(OH)·nH2O)
AI-generated identification · may be incorrectHardness of 4-5.5 on the Mohs scale, typically yellowish-brown to dark brown or black in color, submetallic to earthy luster, amorphous or microcrystalline crystal structure, and a yellowish-brown streak.
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Physical properties
Hardness of 4-5.5 on the Mohs scale, typically yellowish-brown to dark brown or black in color, submetallic to earthy luster, amorphous or microcrystalline crystal structure, and a yellowish-brown streak.
Formation & geological history
Formed as a secondary mineral resulting from the weathering and oxidation of various iron-bearing minerals, often found in gossans, bog iron deposits, and sedimentary iron formations.
Uses & applications
Historically used as a low-grade iron ore and as a pigment (ochre) for paints and ceramics; primarily collected by mineral enthusiasts today.
Geological facts
Limonite is not a distinct mineral species, but rather a natural mixture of related iron oxides and hydroxides like goethite, lepidocrocite, and jarosite.
Field identification & locations
Commonly identified by its distinctive yellowish-brown streak, heavy feel relative to its size, and rusty, earthy appearance. Found worldwide wherever iron-rich rocks undergo weathering.
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Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
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Granite
Granite (Phaneritic intrusive igneous rock)
igneous
Septarian Pebble
Septarian nodule / Concretion
sedimentary