igneous
Granite Cobble
Felsic intrusive igneous rock
Hardness: 6-7 on Mohs scale. Color: predominantly white and grey with black flecks. Luster: Dull (weathered) to vitreous. Crystal structure: Phaneritic (visible crystals). Cleavage: Imperfect. Specific gravity: 2.63-2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- predominantly white and grey with black flecks
- Luster
- Dull (weathered) to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale. Color: predominantly white and grey with black flecks. Luster: Dull (weathered) to vitreous. Crystal structure: Phaneritic (visible crystals). Cleavage: Imperfect. Specific gravity: 2.63-2.75.
Formation & geological history
Formed through the slow cooling of silica-rich magma beneath the Earth's surface. This particular specimen has been rounded by fluvial (river) or glacial transport, likely during the Quaternary period.
Uses & applications
Crushed stone for road construction, architectural stone, and decorative landscaping. High-quality granite is used for countertops and monuments.
Geological facts
Granite makes up a large portion of the Earth's continental crust. The black flecks seen in this specimen are likely biotite mica or hornblende, while the white matrix is primarily quartz and feldspar.
Field identification & locations
Identify by its 'salt and pepper' appearance and hardness (it will scratch glass). Commonly found in riverbeds, glacial moraines, and mountainous regions.
