mineral

Limonite and Goethite

Limonite (hydrated iron(III) oxide-hydroxide) and Goethite (α-FeO(OH))

Hardness: 4.0 - 5.5; Color: Dark brown to yellow-brown, often with rust-like staining; Luster: Dull, earthy to submetallic; Crystal Structure: Amorphous (limonite) or Orthorhombic (goethite); Specific Gravity: 2.7 - 4.3.

Hardness: 4
Color: Dark brown to yellow-brown, often with rust-like staining
Luster: Dull, earthy to submetallic

Identified April 6, 2026More mineral →

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Physical properties

Formation & geological history

Primary formation through the weathering of iron-rich sulfide minerals (like pyrite) or secondary deposition in sedimentary environments, often forming bog iron or gossans.

Uses & applications

Historically used as an important iron ore; currently used primarily as an ocher pigment for coloring paints, cement, and ceramics. Low industrial value in small quantities.

Geological facts

Limonite was once the primary source of 'yellow ocher' used by early humans for cave paintings. It often forms a 'gossan' or 'iron hat' over deeper metal deposits, serving as a signpost for miners.

Field identification & locations

Identify by its brownish-yellow streak (unlike hematite's red streak). It is often found in wet, oxygen-rich environments where iron minerals oxidize. Collectors look for botryoidal shapes which are more aesthetically pleasing.

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