igneous
Granite Cobble
Phaneritic Felsic Igneous Rock
Hardness: 6-7 on Mohs scale; Color: Mottled grey, white, and black; Luster: Dull to vitreous; Structure: Phaneritic (visible crystals of quartz, feldspar, and mica); Shape: Sub-rounded due to water erosion.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled grey, white, and black
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled grey, white, and black; Luster: Dull to vitreous; Structure: Phaneritic (visible crystals of quartz, feldspar, and mica); Shape: Sub-rounded due to water erosion.
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground (plutonic). This specific specimen has been weathered and rounded by fluvial or glacial transport.
Uses & applications
Used primarily as construction aggregate, decorative landscaping stone, and architectural facing. Due to its hardness, it is highly durable.
Geological facts
Granite makes up a large portion of the Earth's continental crust. The pink or white grains are usually feldspar, the clear glassy grains are quartz, and the black specks are usually biotite or hornblende.
Field identification & locations
Identify by its 'salt and pepper' appearance and visible interlocking crystals. It is found globally in mountainous regions or as glacial till in riverbeds.
