mineral

Yellow Ocher / Limonite

FeO(OH)·nH2O (Hydrated iron(III) oxide-hydroxide)

AI-generated identification · may be incorrect

Hardness: 4.0-5.5; Color: Yellow, mustard, ochre-yellow; Luster: Earthy, dull; Crystal structure: Amorphous to microcrystalline; Cleavage: None; Specific Gravity: 2.7-4.3

Hardness: 4
Color: Yellow, mustard, ochre-yellow
Luster: Earthy, dull

Identified May 2, 2026More mineral →

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Physical properties

Hardness: 4.0-5.5; Color: Yellow, mustard, ochre-yellow; Luster: Earthy, dull; Crystal structure: Amorphous to microcrystalline; Cleavage: None; Specific Gravity: 2.7-4.3

Formation & geological history

Formed as secondary deposits primarily through the chemical weathering of iron-rich minerals such as pyrite, magnetite, and hematite in oxidizing conditions.

Uses & applications

Used historically as a natural pigment (yellow ochre) for paints and dyes. Also used as an iron ore of secondary importance and in soil fertilizers.

Geological facts

Yellow ochre is one of the oldest pigments used by humans, appearing in cave paintings dating back over 30,000 years. It is often a component of 'gossan' or iron hats found above ore deposits.

Field identification & locations

Identified in the field by its distinct yellow-brown streak, earthy texture, and tendency to stain fingers yellow. Often found in marshes, lake bottoms, or as a weathering crust on iron-bearing rocks.