igneous
Granite
Granite (phaneritic intrusive igneous rock consisting mainly of quartz, alkali feldspar, and plagioclase)
Hardness: 6-7 Mohs; Color: Gray, salt-and-pepper, or white with black/brown flecks; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible crystals); Specific gravity: 2.65 to 2.75
- Hardness
- 6-7 Mohs
- Color
- Gray, salt-and-pepper, or white with black/brown flecks
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Gray, salt-and-pepper, or white with black/brown flecks; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible crystals); Specific gravity: 2.65 to 2.75
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground (plutonic formation). Age can range from over 3.5 billion years to relatively recent geological periods, but it is a primary constituent of Earth's continental crust.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, and monuments. It is also crushed into aggregate for road building and concrete.
Geological facts
Granite makes up the core of most mountain ranges around the world, like the Sierra Nevada. It is one of the hardest natural stones and is famous for its durability, which is why it was used to build the Great Pyramid of Giza's King's Chamber.
Field identification & locations
Identify in the field by its 'salt-and-pepper' appearance and interlocking visible crystals of white/clear quartz and opaque feldspar. Commonly found in mountainous regions or as glacial erratics in plains. Collectors look for unique coloration or large inclusions.
