igneous
Granite Cobble
Granite (Phaneritic igneous rock composed of Quartz, Feldspar, and Mica)
Hardness: 6–7 on Mohs scale; Color: Mottled gray, white, and black with subtle pink/orange mineral grains; Luster: Vitreous to dull; Crystal structure: Phaneritic (medium-grained crystalline); Specific gravity: 2.63 to 2.75
- Hardness
- 6–7 on Mohs scale
- Luster
- Vitreous to dull
Identified More igneous →
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Physical properties
Hardness: 6–7 on Mohs scale; Color: Mottled gray, white, and black with subtle pink/orange mineral grains; Luster: Vitreous to dull; Crystal structure: Phaneritic (medium-grained crystalline); Specific gravity: 2.63 to 2.75
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. This specific specimen is likely a water-worn or glacial-eroded cobble, giving it its rounded shape. Geological age varies by region but is typically Precambrian to Cenozoic.
Uses & applications
Used in crushed form for road construction and concrete. In its raw form, it is a primary material for countertops, monuments, and landscape architecture. Rough cobbles are often used for decorative garden paths.
Geological facts
Granite is one of the most common rocks in the Earth's continental crust. Its name comes from the Latin word 'granum,' meaning grain, in reference to its coarse-grained texture.
Field identification & locations
Identify in the field by its salt-and-pepper appearance and the presence of visible interlocking crystals that cannot be scratched easily by a steel knife. Commonly found in riverbeds, glacial moraines, and exposed mountain batholiths.
