igneous
Granite
Phaneritic plutonic igneous rock
Hardness: 6-7 (Mohs scale); Color: speckled tan, gray, and black; Luster: dull to vitreous; Crystal structure: phaneritic (visible crystals of quartz, feldspar, and biotite).
- Hardness
- 6-7 (Mohs scale)
- Color
- speckled tan, gray, and black
- Luster
- dull to vitreous
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Physical properties
Hardness: 6-7 (Mohs scale); Color: speckled tan, gray, and black; Luster: dull to vitreous; Crystal structure: phaneritic (visible crystals of quartz, feldspar, and biotite).
Formation & geological history
Granite forms from the slow crystallization of magma below Earth's surface (intrusive). It is found in continental crust and often dates back to various tectonic mountain-building events throughout Earth's history.
Uses & applications
Used extensively in construction (curbstones, floor tiles), kitchen countertops, monuments, and as crushed stone for road aggregate. Smaller pebbles are common in landscaping.
Geological facts
Granite is one of the hardest and most durable stones, which is why it is used for monuments like Mount Rushmore. It makes up a large portion of the Earth's continental crust.
Field identification & locations
Identify in the field by its speckled 'salt and pepper' appearance and visible crystalline texture. It is ubiquitous in mountainous regions and riverbeds.
