igneous
Granite
Granite (Phaneritic intrusive igneous rock)
Hardness: 6-7 on Mohs scale. Color: Mottled salt-and-pepper (white, gray, pink, black). Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained, visible crystals). Cleavage: Varies by constituent mineral (none for quartz, excellent for mica). Specific gravity: 2.65-2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled salt-and-pepper (white, gray, pink, black)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Mottled salt-and-pepper (white, gray, pink, black). Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained, visible crystals). Cleavage: Varies by constituent mineral (none for quartz, excellent for mica). Specific gravity: 2.65-2.75.
Formation & geological history
Formed by the slow crystallization of magma below Earth's surface (plutonic). Typically formed in continental crust during orogenic (mountain-building) events. Age ranges from billions of years (Precambrian) to relatively recent.
Uses & applications
Extensively used in construction as dimension stone, countertops, flooring, curbing, and crushed stone for road base and concrete. Higher quality specimens used in 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 common stones, making it the preferred material for kitchen countertops and public monuments like Mount Rushmore.
Field identification & locations
Identify in the field by its interlocking, coarse-grained crystals of quartz (clear/gray), feldspar (white/pink), and mica (shiny black/silver). Found in mountain ranges and eroded shield areas globally, such as the Appalachians or the Sierra Nevadas.
