igneous
Limonite-stained Granite
Felsic Plutonic Rock with Hydrated Iron Oxides
Hardness: 6-7 (Mohs); Color: Pinkish-red base with yellow-orange limonite staining; Luster: Dull to vitreous; Structure: Phaneritic (medium-grained crystals) including quartz, orthoclase feldspar, and biotite mica; Specific Gravity: 2.63-2.75
- Hardness
- 6-7 (Mohs)
- Color
- Pinkish-red base with yellow-orange limonite staining
- Luster
- Dull to vitreous
Identified More igneous →
Explore Limonite-stained Granite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 (Mohs); Color: Pinkish-red base with yellow-orange limonite staining; Luster: Dull to vitreous; Structure: Phaneritic (medium-grained crystals) including quartz, orthoclase feldspar, and biotite mica; Specific Gravity: 2.63-2.75
Formation & geological history
Formed through slow crystallization of magma below Earth's surface. The orange-yellow surface is a secondary weathering effect where iron-bearing minerals (like biotite or pyrite) oxidize into limonite in the presence of water and oxygen.
Uses & applications
Granite is used extensively in construction, countertops, and decorative gravel. Iron-oxide stained versions are often used in landscaping or for geological study of weathering processes.
Geological facts
Limonite was once used as a primary yellow pigment for paints and is one of the oldest known pigments used by humans for cave drawings. The pink/red color of the rock itself suggests high potassium feldspar content.
Field identification & locations
Identify by its crystalline texture and the way the yellow-orange coating can often be scratched or found localized to joints and surfaces. Commonly found in batholiths and continental crustal shields.
