igneous
Granite
Phaneritic Plutonic Felsic Rock (SiO2 > 69%)
Hardness: 6-7 Mohs; Color: Pink, white, and gray with dark speckles; Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained); Cleavage: Distinct in feldspar grains; Specific Gravity: 2.63-2.75
- Hardness
- 6-7 Mohs
- Color
- Pink, white, and gray with dark speckles
- Luster
- Dull to vitreous
Identified More igneous →
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Physical properties
Hardness: 6-7 Mohs; Color: Pink, white, and gray with dark speckles; Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained); Cleavage: Distinct in feldspar grains; Specific Gravity: 2.63-2.75
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. This specimen appears to be a water-worn or weathered pebble likely from a continental crust source of varying geological ages (Proterozoic to Cenozoic).
Uses & applications
Used widely in construction for countertops, floor tiles, paving stones, curbing, monuments, and as crushed stone or aggregate.
Geological facts
Granite is the most common rock found in the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in the Black Hills of South Dakota.
Field identification & locations
Identify in the field by its visible interlocking crystals of varied colors (quartz, feldspar, and mica). It is found globally in mountainous regions and areas where old crust is exposed. Look for the characteristic 'salt and pepper' appearance.
