igneous
Granite Pebble
Granite (Plutonic Igneous Rock)
Hardness: 6-7 on Mohs scale; Color: Pinkish-brown with dark gray/black patches and whitish inclusions; Luster: Dull to sub-vitreous; Texture: Phaneritic (coarse-grained, visible intergrown crystals); Cleavage: Indistinct due to intergrown grains.
- Hardness
- 6-7 on Mohs scale
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pinkish-brown with dark gray/black patches and whitish inclusions; Luster: Dull to sub-vitreous; Texture: Phaneritic (coarse-grained, visible intergrown crystals); Cleavage: Indistinct due to intergrown grains.
Formation & geological history
Formed through the slow crystallization of felsic magma beneath the Earth's surface (intrusive igneous). This particular specimen has been smoothed and rounded by river or glacial erosion, turning it into a beach/river pebble.
Uses & applications
Crushed granite is used in construction and landscaping. Intact polished stones are used for decorative landscaping, lapidary art, and rock tumbling.
Geological facts
Granite makes up a large portion of the Earth's continental crust. The pinkish color comes from potassium feldspar (orthoclase), while the dark grains consist of biotite mica or amphibole, and clear/white parts are quartz.
Field identification & locations
Identify in the field by its visible multi-colored interlocking mineral grains (mottled pink, black, and white) and rounded, water-worn shape. Highly abundant in gravel beds, glacial till, and riverbeds worldwide.
