igneous
Red Granite
Phaneritic Plutonic Rock (High Potassium Feldspar)
Hardness: 6-7 (Mohs scale); Color: Pink to reddish-orange with black and translucent grains; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained crystals visible to the naked eye); Cleavage: Perfect in two directions for feldspar components; Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 (Mohs scale)
- Color
- Pink to reddish-orange with black and translucent grains
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Pink to reddish-orange with black and translucent grains; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained crystals visible to the naked eye); Cleavage: Perfect in two directions for feldspar components; Specific gravity: 2.63 to 2.75
Formation & geological history
Formed from the slow cooling and crystallization of silica-rich magma deep underground (plutonic). The reddish hue is caused by a high concentration of potassium-rich orthoclase feldspar. Geological ages vary widely from Precambrian to Cenozoic eras.
Uses & applications
Extensively used as a building material, dimension stone for monuments, kitchen countertops, and as crushed stone for road construction and railroad ballast.
Geological facts
The red color often indicates a terrestrial or 'S-type' granite origin. Some of the most famous red granites come from Aswan, Egypt, and were used by ancient civilizations to construct obelisks and the inner chambers of pyramids.
Field identification & locations
Identify in the field by its speckled, 'salt and pepper' appearance with prominent pink/red minerals. It will not react with acid like limestone and is hard enough to scratch glass. Found globally in continental crust, particularly in mountain ranges and Canadian Shield areas.
