igneous
Granite Cobble
Granitoid (composed mainly of Quartz, Feldspar, and Mica)
Hardness: 6-7 on Mohs scale; Color: Mottled pink, grey, and white; Luster: Dull (weathered) to vitreous; Crystal structure: Phaneritic (visible grains); Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled pink, grey, and white
- Luster
- Dull (weathered) to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled pink, grey, and white; Luster: Dull (weathered) to vitreous; Crystal structure: Phaneritic (visible grains); Specific gravity: 2.63 to 2.75
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. This specific specimen has been rounded by fluvial (river) or glacial transport, likely during the Quaternary period.
Uses & applications
Used primarily in construction, road base, landscaping, and architectural veneers. Higher quality slabs are used for countertops.
Geological facts
Granite makes up a large portion of the Earth's continental crust. It is one of the hardest and most durable common stones, which is why it is used for monuments such as Mount Rushmore.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals of quartz and feldspar. Commonly found in riverbeds or glacial tills in continental regions.
