igneous
Granite River Pebble
Phaneritic Felsic Igneous Rock (Granite)
Hardness: 6-7 Mohs; Color: Pinkish-orange, tan, and black; Luster: Dull to vitreous (waxy when wet); Structure: Crystalline phaneritic; Cleavage: None (fractures); Specific Gravity: 2.63-2.75
- Hardness
- 6-7 Mohs
- Color
- Pinkish-orange, tan, and black
- Luster
- Dull to vitreous (waxy when wet)
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Physical properties
Hardness: 6-7 Mohs; Color: Pinkish-orange, tan, and black; Luster: Dull to vitreous (waxy when wet); Structure: Crystalline phaneritic; Cleavage: None (fractures); Specific Gravity: 2.63-2.75
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground, typically during the Precambrian or Paleozoic eras. This specimen shows significant rounding from fluvial (river) or glacial transport.
Uses & applications
Used primarily for landscaping, decorative gravel, construction aggregate, and occasionally for rock tumbling by hobbyists.
Geological facts
The pinkish-orange color is due to a high concentration of potassium feldspar (orthoclase). Granite makes up the majority of the Earth's continental crust.
Field identification & locations
Identifiable by its 'salt and pepper' crystalline texture and hardness (it will scratch glass). Commonly found in riverbeds, glacial till, and mountainous outcrops.
