igneous
Granite River Cobble
Granitoid (comprising Quartz, Feldspar, and Mica)
Hardness: 6-7 Mohs; Color: Pinkish-red, tan, and grey phaneritic texture; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.63-2.75
- Hardness
- 6-7 Mohs
- Color
- Pinkish-red, tan, and grey phaneritic texture
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Pinkish-red, tan, and grey phaneritic texture; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.63-2.75
Formation & geological history
Formed through slow crystallization of magma below Earth's surface. This specific specimen has been physically weathered and rounded into a cobble shape by water transport in a river or glacial environment.
Uses & applications
Used in construction, landscaping, road base, and occasionally polished for decorative river rock features.
Geological facts
Granite is the most common igneous rock of the Earth's crust. Its pink color usually indicates a high concentration of potassium feldspar (orthoclase).
Field identification & locations
Identify in the field by its 'salt and pepper' or interlocking crystalline appearance and its extreme hardness. It won't be scratched by a steel knife.
