igneous
Granite Cobble
Granitoid
Hardness: 6-7 (Mohs); Color: Tan, grey, speckled black; Luster: Dull (weathered); Crystal structure: Phaneritic (visible grains); Cleavage: None (fractures); Specific Gravity: 2.63-2.75
- Hardness
- 6-7 (Mohs)
- Color
- Tan, grey, speckled black
- Luster
- Dull (weathered)
Identified More igneous →
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Physical properties
Hardness: 6-7 (Mohs); Color: Tan, grey, speckled black; Luster: Dull (weathered); Crystal structure: Phaneritic (visible grains); Cleavage: None (fractures); Specific Gravity: 2.63-2.75
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground. This specimen appears water-worn or weathered into a rounded cobble shape, likely transported by fluvial or glacial activity.
Uses & applications
Primarily used in construction as aggregate or building stone. Small rounded specimens are often used in landscaping or as aquarium decor.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Because it is resistant to erosion, it often forms the core of major mountain ranges.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and hardness (it will jump or spark against steel). Commonly found in riverbeds or gravel pits in regions with igneous bedrock.
