igneous
Granite
Granite (Phaneritic intrusion / SiO2 + KAlSi3O8 + NaAlSi3O8)
Hardness: 6-7 Mohs; Color: Gray, salt-and-pepper, or white mottled with black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible crystals); Specific gravity: 2.63 to 2.75.
- Hardness
- 6-7 Mohs
- Color
- Gray, salt-and-pepper, or white mottled with black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Gray, salt-and-pepper, or white mottled with black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible crystals); Specific gravity: 2.63 to 2.75.
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface (plutonic). It is primarily composed of quartz, feldspar, and mica. Geological age ranges from the Archean Eon to the Cenozoic Era depending on location.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, curbing, and monuments. It is also a source for dimension stone and crushed stone aggregate.
Geological facts
Granite makes up a large portion of the Earth's continental crust. El Capitan in Yosemite National Park is one of the most famous exposed granite monoliths in the world. It is highly resistant to acid rain and weathering.
Field identification & locations
Identify by its interlocking 'salt-and-pepper' appearance where quartz and feldspar grain boundaries are easily visible to the naked eye. Common across continental shields and mountain ranges. Collectors look for unique large-crystal varieties like pegmatites.
