igneous
Granite
Phaneritic intrusive igneous rock (Composition: Quartz, Feldspar, Mica)
Hardness: 6-7 Mohs; Color: Pinkish-tan with black biotite spots; Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained) crystalline; Cleavage: None (fractures)
- Hardness
- 6-7 Mohs
- Color
- Pinkish-tan with black biotite spots
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Pinkish-tan with black biotite spots; Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained) crystalline; Cleavage: None (fractures)
Formation & geological history
Formed by the slow crystallization of magma below Earth's surface. These specimens are often millions to billions of years old and frequently rounded by river or glacial transport.
Uses & applications
Used extensively in construction (countertops, flooring), monuments, curbing, and as aggregate. Polished specimens are used for decorative purposes.
Geological facts
Granite makes up a large portion of the Earth's continental crust. It is one of the hardest and most durable natural stones, which is why it is used for Egyptian pyramids and modern skyscrapers alike.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals of quartz and feldspar. Commonly found in mountainous regions or as glacial erratics in riverbeds.
