igneous
Granite cobble
Granite
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (white, grey, and pink tones). Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained visible crystals). Major minerals: Quartz, Feldspar, and Mica. Specific gravity: 2.63 - 2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Salt-and-pepper (white, grey, and pink tones)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (white, grey, and pink tones). Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained visible crystals). Major minerals: Quartz, Feldspar, and Mica. Specific gravity: 2.63 - 2.75.
Formation & geological history
Formed from the slow crystallization of magma below the Earth's surface. This specimen appears to be a stream-rounded cobble, likely of intrusive origin from the Phanerozoic eon, shaped by water erosion in a river or glacial environment.
Uses & applications
Used extensively in construction for countertops, floor tiles, and paving stones. In crushed form, used as road base and railway ballast. High polish grade specimens are used in monuments and memorials.
Geological facts
Granite is one of the hardest substances in the world, second only to diamonds. It makes up a large portion of the Earth's continental crust and is frequently found in the core of mountain ranges.
Field identification & locations
Identified by its speckled appearance and visible interlocking crystals of quartz and feldspar. Commonly found in riverbeds, glacial tills, and mountain outcrops. It will not react with acid and is hard enough to scratch glass.
