igneous
Granite Cobble
Phaneritic Felsic Intrusive Rock (Granite)
Hardness: 6-7 on Mohs scale; Color: Mottled pink, white, and grey; Luster: Dull (weathered) to vitreous; Structure: Phaneritic (visible crystals); Composition: Quartz, Potassium Feldspar, and Plagioclase.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled pink, white, and grey
- Luster
- Dull (weathered) to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled pink, white, and grey; Luster: Dull (weathered) to vitreous; Structure: Phaneritic (visible crystals); Composition: Quartz, Potassium Feldspar, and Plagioclase.
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground. This specific specimen is likely a water-worn cobble or river stone from the Holocene epoch, derived from older Precambrian or Paleozoic plutons.
Uses & applications
Granite is primarily used as a construction material for countertops, flooring, and road aggregate. Rounded river cobbles like this are used in landscaping and aquarium decor.
Geological facts
Granite is the most common rock type found in the Earth's continental crust. Its durability is so high that it was used by Ancient Egyptians to build pyramids and statues that still stand today.
Field identification & locations
Identify by its 'salt and pepper' or multicrystalline appearance and its high hardness (it will scratch glass). Commonly found in riverbeds, glacial deposits, and mountain outcrops.
