igneous/metamorphic
Granitoid (Granite/Gneiss mix)
Granite or Granitic Gneiss (Silicon dioxide SiO2 with Al, K, Na silicates)
Hardness: 6-7 (Mohs scale), Color: Salt and pepper (gray, white, pink, black), Luster: Vitreous to dull, Crystal structure: Phaneritic or foliated, Cleavage: Poor, Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 6-7 (Mohs scale), Color: Salt and pepper (gray, white, pink, black), Luster: Vitreous to dull, Crystal structure: Phaneritic or foliated, Cleavage: Poor, Specific Gravity: 2.6-2.7
Formation & geological history
Formed through slow crystallization of magma below Earth's surface (igneous) or through intense heat and pressure (metamorphic), dating back to various geological periods including the Precambrian.
Uses & applications
Used widely in construction (countertops, floor tiles), architectural facing, road crushed stone, and landscaping.
Geological facts
Granite is the most common rock found in the Earth's continental crust. It forms the base of many mountain ranges, such as the Sierra Nevada and the Himalayas.
Field identification & locations
Identify by its interlocking grains of quartz, feldspar, and dark minerals (mica/amphibole). Found globally in continental shields and mountain belts. Collectors look for unique large crystals or banding.
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