igneous
Granite
Intrusive Phaneritic Felsic Igneous Rock
Hardness: 6-7 on Mohs scale. Color: Salt and pepper appearance with shades of white, pink, grey, and black. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained) with visible crystals of quartz (clear/grey), feldspar (white/pink), and mica/amphibole (black).…
- Hardness
- 6-7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Salt and pepper appearance with shades of white, pink, grey, and black. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained) with visible crystals of quartz (clear/grey), feldspar (white/pink), and mica/amphibole (black). Cleavage: Imperfect (varies by mineral component). Specific gravity: 2.63 to 2.75.
Formation & geological history
Formed by the slow crystallization of magma below Earth's surface (plutonic). Most granite formations are millions to billions of years old (Precambrian to Cenozoic). Formed in continental crust zones.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, and monuments. Used as crushed stone for road base and concrete aggregate. Highly valued by collectors for specimens containing large garnets or tourmalines.
Geological facts
Granite makes up the bulk of Earth's continental crust. Mount Rushmore is carved into a massive granite batholith. It is one of the hardest and most durable common stones, resistant to acids and scratching.
Field identification & locations
Identify in the field by its coarse crystalline texture where grains are visible to the naked eye; it will not have layers like gneiss or small pores like basalt. Common in mountain ranges and crystalline shield areas. Collectors should look for unique mineral inclusions or large crystals.
