igneous
Granite Cobble
Granite (Felsic Plutonic Rock)
Hardness: 6-7 on Mohs scale; Color: Salt and pepper (white, gray, black, pink); Luster: Phaneritic (crystalline); Texture: Granular; Specific Gravity: 2.63 - 2.75; Composition: Quartz, Feldspar, and Biotite/Mica.
- Hardness
- 6-7 on Mohs scale
- Color
- Salt and pepper (white, gray, black, pink)
- Luster
- Phaneritic (crystalline)
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Salt and pepper (white, gray, black, pink); Luster: Phaneritic (crystalline); Texture: Granular; Specific Gravity: 2.63 - 2.75; Composition: Quartz, Feldspar, and Biotite/Mica.
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface. This specific specimen has been chemically and physically weathered into a rounded cobble, likely transported by water or glacial activity. Granite can date from the Precambrian to the Cenozoic eras.
Uses & applications
Used widely in construction (countertops, flooring, monuments), as crushed stone for road aggregate, and as landscaping stones. Small river-worn cobbles are popular in decorative garden arrangements.
Geological facts
Granite makes up a large part of the continental crust. It is one of the hardest and most durable common stones, which is why it has been used for everything from Egyptian pyramids to modern skyscrapers.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals of diverse colors. It will not be scratched by a steel nail. Commonly found in mountainous regions or as glacial till in riverbeds.
