igneous
Granite
Granite (compositional mixture of Quartz, Feldspar, and Mica)
Hardness: 6-7 on Mohs scale; Color: Mottled grey, white, and tan; Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained crystalline); Cleavage: None (individual minerals within have cleavage, but the rock fractures irregularly).
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled grey, white, and tan
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Mottled grey, white, and tan; Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained crystalline); Cleavage: None (individual minerals within have cleavage, but the rock fractures irregularly).
Formation & geological history
Formed from the slow crystallization of silica-rich magma below the Earth's surface (intrusive). Geological age varies globally from Archean to Cenozoic eras.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, curbing, and as aggregate in road building. Also used for monuments and sculptures.
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 has been used since Ancient Egypt for massive obelisks and temple structures.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. It is ubiquitous in mountain ranges and continental shields. Collectors should look for specimens with large phenocrysts or unusual mineral inclusions.
