igneous
Granite Pebble
Granite (Plutonic Igneous Rock)
Hardness: 6-7 on Mohs scale. Color: Mottled pink, tan, grey, and black. Luster: Vitreous to dull (polished surface). Texture: Phaneritic (coarse-grained coarse crystalline structure). Cleavage: Variable depending on individual mineral grains.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled pink, tan, grey, and black
- Luster
- Vitreous to dull (polished surface)
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Mottled pink, tan, grey, and black. Luster: Vitreous to dull (polished surface). Texture: Phaneritic (coarse-grained coarse crystalline structure). Cleavage: Variable depending on individual mineral grains.
Formation & geological history
Formed from the slow cooling and crystallization of silica-rich magma deep underground (plutonic environment). Smooth, rounded shape indicates erosion and weathering by water or glacial transport followed by tumbling/polishing.
Uses & applications
Commonly used as decorative river stones, landscaping, aquarium gravel, tumbling practice for lapidary hobbyists, and general geological specimens.
Geological facts
Granite makes up a large portion of the Earth's continental crust. The distinct speckled appearance comes from a blend of quartz, potassium feldspar, plagioclase feldspar, and dark biotite mica or hornblende.
Field identification & locations
Easily identified by its speckled, coarse-grained texture containing visible interlocking crystals of quartz (clear/grey glassy areas), feldspar (pink/tan blocky grains), and mica (black specks). Very abundant along riverbeds, beaches, and glacial deposits worldwide.
