igneous
Granite Cobble
Phaneritic Felsic Igneous Rock
Hardness: 6-7 on Mohs scale; Color: Mottled grey, pink, and white; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained visible crystals); Composition: Quartz, Feldspar, and Mica.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled grey, pink, and white
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled grey, pink, and white; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained visible crystals); Composition: Quartz, Feldspar, and Mica.
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface. These specific rounded shapes are produced by fluvial (river) or glacial erosion over thousands of years.
Uses & applications
Commonly used for landscaping, decorative garden borders, architectural accents, and historically for paving as cobblestones.
Geological facts
Granite is one of the hardest and most common rocks in the Earth's continental crust. Because it is resistant to weathering, it is frequently found as river stones.
Field identification & locations
Identify by its interlocking 'salt and pepper' crystalline texture and extreme hardness (cannot be scratched by a steel knife). Commonly found in riverbeds and glacial tills.
