igneous
Granite
Granite (Felsic Intrusive Igneous Rock)
Hardness: 6-7 Mohs; Color: Pinkish-tan with black and grey inclusions; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarsegrained/visible crystals); Composition: Quartz, Feldspar, and Mica (Biotite).
- Hardness
- 6-7 Mohs
- Color
- Pinkish-tan with black and grey inclusions
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Pinkish-tan with black and grey inclusions; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarsegrained/visible crystals); Composition: Quartz, Feldspar, and Mica (Biotite).
Formation & geological history
Formed through the slow crystallization of magma below the Earth's surface. This specimen appears weathered or river-worn, likely originating from a batholith of Paleozoic or Precambrian age depending on the locality.
Uses & applications
Used extensively in construction for countertops, floor tiles, paving stone, curbing, and as a decorative architectural finish. High-quality specimens are used in landscaping.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a massive granite outcrop. It is one of the hardest and most durable common stones.
Field identification & locations
Identify in the field by its speckled 'salt and pepper' appearance and visible interlocking crystals. Common in mountain ranges and glacial till. Collectors look for large crystals or unique color variations.
