igneous
Granite
Phaneritic Plutonic Felsic Rock (KAlSi3O8 - SiO2 - NaAlSi3O8)
Hardness: 6-7 on Mohs scale. Color: mottled pink, red, gray, and black. Luster: vitreous to dull. Crystal structure: coarse-grained phaneritic. Cleavage: non-existent (breaks irregularly). Specific gravity: 2.63 - 2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- mottled pink, red, gray, and black
- Luster
- vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale. Color: mottled pink, red, gray, and black. Luster: vitreous to dull. Crystal structure: coarse-grained phaneritic. Cleavage: non-existent (breaks irregularly). Specific gravity: 2.63 - 2.75.
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface. This specimen shows a high concentration of potassium feldspar (pink/orange) and biotite mica (black streaks). Formation occurs over millions of years in continental crust.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, and monuments. Also used as crushed stone for road base and railroad ballast.
Geological facts
Granite makes up the majority of the Earth's continental crust. Because it is so hard and durable, it is often used for curling stones and memorials that need to withstand centuries of weathering.
Field identification & locations
Identify in the field by its 'salt and pepper' or multicrystalline appearance where individual mineral grains (quartz, feldspar, mica) are visible to the naked eye. Found globally in mountain ranges and continental shields.
