mineral

Limonite or Ironstone

Hydrated iron oxide-hydroxide, approximately FeO(OH)·n(H2O)

AI-generated identification · may be incorrect

Hardness: 4-5.5 on the Mohs scale; Color: Yellow-brown, dark brown, to blackish; Luster: Earthy, submetallic, or silky; Crystal structure: Amorphous or microcrystalline, typically forms as stalactitic, mammillary, or massive crusts; Cleavage: None; Specific Gravity: 2.7-4.3

Hardness: 4-5
Color: Yellow-brown, dark brown, to blackish
Luster: Earthy, submetallic, or silky

Identified August 3, 2026More mineral →

Explore Limonite or Ironstone in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed as a secondary mineral resulting from the oxidation and weathering of various iron-bearing minerals, commonly occurring in gossans (iron hats), bog iron deposits, and sedimentary iron ores.

Uses & applications

Historically used as an iron ore, a yellow-brown pigment (ochre) in paints, and occasionally cut into cabochons or collected by mineral enthusiasts.

Geological facts

Limonite is not a true distinct mineral species, but rather a mixture of related hydrated iron oxides, most commonly goethite, lepidocrocite, and jarosite.

Field identification & locations

Easily identified by its characteristic yellowish-brown streak on an unglazed porcelain plate. Found worldwide, especially in weathered iron deposits and oxidizing zones of sulfide ore bodies.