igneous
Granite
Granite (Felsic Plutonic Rock)
Hardness: 6-7 on Mohs scale. Color: Mottled gray, white, pink, and black. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained) interlocking crystals. Cleavage: Indistinct. Specific gravity: 2.63 to 2.75.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled gray, white, pink, and black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Mottled gray, white, pink, and black. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained) interlocking crystals. Cleavage: Indistinct. Specific gravity: 2.63 to 2.75.
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface (intrusive). Most granites date from the Precambrian to more recent geological eras and form in continental crust above subduction zones.
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 is the most common igneous rock found on Earth's continents and makes up the core of many mountain ranges. It is the official state rock of several US states, including New Hampshire (The Granite State) and Vermont.
Field identification & locations
Identify by its 'salt and pepper' appearance and visible interlocking crystals of quartz, feldspar, and mica. It is commonly found in mountainous regions or areas where ancient crust is exposed. It will not scratch with a copper penny or steel knife easily.
