igneous
Granite Pebble
Granite (Plutonic Igneous Rock)
Hardness: 6-7 on Mohs scale. Color: Mottled grey, pinkish-tan, and dark green/black. Luster: Dull to vitreous on fresh surfaces. Texture: Phaneritic (medium-grained, visibly crystalline), stream-rounded pebble shape with a visible fracture or joint line.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled grey, pinkish-tan, and dark green/black
- Luster
- Dull to vitreous on fresh surfaces
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Mottled grey, pinkish-tan, and dark green/black. Luster: Dull to vitreous on fresh surfaces. Texture: Phaneritic (medium-grained, visibly crystalline), stream-rounded pebble shape with a visible fracture or joint line.
Formation & geological history
Formed through the slow cooling and crystallization of felsic magma deep beneath the Earth's surface (intrusive igneous environment). Later exposed by uplift, weathering, and rounded by fluvial or glacial water erosion.
Uses & applications
Commonly used as construction aggregate, crushed stone, road base, landscaping rock, and decorative river rock.
Geological facts
Granite makes up a major portion of the Earth's continental crust. The distinct speckled texture is due to the intergrown individual mineral grains of quartz, potassium feldspar, plagioclase, and biotite mica or amphibole.
Field identification & locations
Look for a granular, speckled pattern with interlocking interlocking crystals of quartz and feldspar, often worn smooth into river pebbles. Commonly found along riverbeds, lakeshores, glacial tills, and mountainous areas worldwide.
