igneous
Granite
Phaneritic Plutonic Felsic Rock (Quartz/Feldspar/Mica)
AI-generated identification · may be incorrectHardness: 6-7 on Mohs scale; Color: Pinkish-orange (K-feldspar), translucent gray (quartz), and black (biotite/hornblende); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pinkish-orange (K-feldspar), translucent gray (quartz), and black (biotite/hornblende); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.63 to 2.75
Formation & geological history
Formed by the slow crystallization of silica-rich magma below the Earth's surface. This specimen appears weathered/water-worn, indicating it was likely transported by water or glacial activity. Granite is a major component of the continental crust, potentially ranging from hundreds of millions to over a billion years old.
Uses & applications
Used extensively in construction for countertops, floor tiles, and monuments due to its durability. Smaller gravel-sized pieces are used as road salt/traction and in railroad ballast.
Geological facts
Granite makes up much of the foundation of the world's continents. It is one of the hardest and most common rocks on Earth. The pink/orange color in this specimen is caused by Potassium Feldspar (Orthoclase).
Field identification & locations
Identified in the field by its speckled 'salt and pepper' appearance and visible interlocking crystals. It is found in mountainous regions or areas with glacial deposits. For collectors, look for the glassy look of quartz versus the blocky cleavage of feldspar within the matrix.
