igneous
Granite / Granodiorite River Pebble
Intrusive Felsic/Intermediate Igneous Rock (Granite / Granodiorite)
AI-generated identification · may be incorrectHardness: 6 - 7 on Mohs scale; Color: Mottled grey, white, and dark greenish-black; Luster: Dull to vitreous on freshly broken surfaces; Texture: Phaneritic (medium-grained), water-worn and sub-rounded cobble; Specific Gravity: ~2.65 - 2.75
- Hardness
- 6 - 7 on Mohs scale
- Color
- Mottled grey, white, and dark greenish-black
- Luster
- Dull to vitreous on freshly broken surfaces
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Physical properties
Hardness: 6 - 7 on Mohs scale; Color: Mottled grey, white, and dark greenish-black; Luster: Dull to vitreous on freshly broken surfaces; Texture: Phaneritic (medium-grained), water-worn and sub-rounded cobble; Specific Gravity: ~2.65 - 2.75
Formation & geological history
Formed through slow crystallization of silica-rich magma deep within the Earth's crust (plutonic environment). Over millions of years, erosion exposed the pluton, and mechanical weathering and transport by rivers or glacial melt rounded the stone into a smooth pebble.
Uses & applications
Commonly used in crushed stone aggregate, architectural stone, road base, and decorative landscaping. Single naturally rounded pebbles are frequently kept as pocket stones, paperweights, or landscape features.
Geological facts
Granite makes up a major portion of Earth's continental crust. Over extensive fluvial transport, soft minerals weather away first, leaving durable interlocking quartz and feldspar grains intact.
Field identification & locations
Identified by its visible interlocking crystalline texture of light minerals (quartz, feldspar) and scattered dark minerals (biotite, hornblende/amphibole), along with its high hardness (scratches glass). Abundantly found along riverbeds, beaches, and glacial gravel deposits worldwide.
