igneous
Granite
Granite (Phaneritic igneous rock)
Hardness: 6-7 on Mohs scale. Color: Gray, tan, and white with dark flecks. Luster: Vitreous to dull. Crystal structure: Macro-crystalline (phaneritic texture). Specific gravity: 2.63-2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Gray, tan, and white with dark flecks
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Gray, tan, and white with dark flecks. Luster: Vitreous to dull. Crystal structure: Macro-crystalline (phaneritic texture). Specific gravity: 2.63-2.75.
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface (intrusive). Geological ages vary significantly from Precambrian to Cenozoic depending on the tectonic location.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, curbing, and monuments. Also used as crushed stone for road base and railroad ballast.
Geological facts
Granite makes up a large portion of the continental crust. Because it is so hard and durable, it has been used for some of the world's most famous structures, including the Great Pyramid of Giza (casing stones) and Mount Rushmore.
Field identification & locations
Identify in the field by its visible interlocking crystals of quartz (clear/gray), feldspar (white/pinkish), and mica (black/shiny). It is found in mountain ranges and continental shields worldwide.
