igneous
Granite Pebble
Granite (Felsic Intrusive Igneous Rock)
Hardness: 6-7 on Mohs scale. Colors: Mottled white, pink, and black. Luster: Vitreous to dull. Structure: Phaneritic (coarse-grained crystals). Cleavage: Varies by mineral constituent. Specific gravity: 2.63-2.75.
- Hardness
- 6-7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale. Colors: Mottled white, pink, and black. Luster: Vitreous to dull. Structure: Phaneritic (coarse-grained crystals). Cleavage: Varies by mineral constituent. Specific gravity: 2.63-2.75.
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. This specific specimen has been tumbled and rounded by water action in a river or coastal environment, likely dating back hundreds of millions of years in its primary formation.
Uses & applications
Used widely in construction (countertops, tiles), as aggregate in road building, and as ornamental stone. Smooth river-worn pebbles are popular for landscaping and aquarium decoration.
Geological facts
Granite makes up much of the continental crust. The pink/orange hues come from Potassium Feldspar, while the white is Quartz and the black bits are usually Biotite mica or Hornblende.
Field identification & locations
Identify by its 'salt and pepper' appearance and visible interlocking crystals. Look for smooth, rounded shapes on beaches or in riverbeds where geological erosion has occurred.
