igneous
Granite Pebble
Granite (Felsic Intrusive Igneous Rock)
Hardness: 6-7 Mohs; Color: Salt and pepper appearance with grey, white, pink, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible crystals); Cleavage: None (fractures irregularly); Specific gravity: 2.63-2.75.
- Hardness
- 6-7 Mohs
- Color
- Salt and pepper appearance with grey, white, pink, and black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper appearance with grey, white, pink, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible crystals); Cleavage: None (fractures irregularly); Specific gravity: 2.63-2.75.
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface. This specimen appears to be a water-worn or tumbled pebble, likely formed millions of years ago in a batholith before being eroded and rounded by river or glacial action.
Uses & applications
Used extensively in construction (countertops, tiles), as aggregate in road building, and in landscaping. Polished pebbles are often used in decorative garden features or aquariums.
Geological facts
Granite makes up a large part of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in the Black Hills of South Dakota.
Field identification & locations
Identify by its interlocking crystal texture and the presence of quartz (grey/glassy), feldspar (white/pink), and mica or hornblende (black spots). Common in mountainous regions and riverbeds.
