mineral

Limonite Nodules / Goethite

Hydrated Iron Oxide-Hydroxide (FeO(OH)·nH2O / Fe2O3·nH2O)

AI-generated identification · may be incorrect

Hardness: 4.0 - 5.5 on the Mohs scale. Color: Yellowish-brown, ochre, dark brown to black. Luster: Earthy, submetallic, to silky. Crystal structure: Amorphous or microcrystalline (pseudomorphous after other minerals). Cleavage: None (fractures unevenly). Specific gravity: 2.7 - 4.3.

Hardness: 4
Color: Yellowish-brown, ochre, dark brown to black
Luster: Earthy, submetallic, to silky

Identified August 1, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the secondary weathering and oxidation of primary iron-bearing minerals (like pyrite, magnetite, or siderite) in hydrothermal veins, sedimentary iron formations, and soil profiles.

Uses & applications

Historically used as a natural mineral pigment (yellow ochre, umber), as a low-grade iron ore, and collected by rockhounds as botryoidal or nodular mineral specimens.

Geological facts

Limonite is not a true discrete mineral species, but rather a natural aggregate of related hydrated iron oxides, most commonly goethite and lepidocrocite. It often forms striking botryoidal, mammillary, or stalactitic crusts and nodules.

Field identification & locations

Easily identified in the field by its characteristic yellowish-brown to rust-brown streak on an unglazed porcelain plate. Found worldwide, including weathering zones in iron-rich geological regions of South America.