igneous
Red Granite
Phaneritic Felsic Intrusive Igneous Rock
Mohs hardness: 6-7; Color: Reddish-pink with black and grey specks; Luster: Dull to vitreous; Crystal structure: Phaneritic (medium-to-coarse grained); Cleavage: Imperfect; Specific gravity: 2.63-2.75
- Hardness
- 6-7
- Color
- Reddish-pink with black and grey specks
- Luster
- Dull to vitreous
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Physical properties
Mohs hardness: 6-7; Color: Reddish-pink with black and grey specks; Luster: Dull to vitreous; Crystal structure: Phaneritic (medium-to-coarse grained); Cleavage: Imperfect; Specific gravity: 2.63-2.75
Formation & geological history
Formed by the slow crystallization of magma below Earth's surface. The red color is due to a high concentration of potassium-rich alkali feldspar (orthoclase) tinted by iron oxides. Common in ancient continental shields.
Uses & applications
Used extensively in construction for countertops, floor tiles, paving stones, and memorial monuments. Its durability makes it ideal for high-traffic surfaces.
Geological facts
Granite makes up the majority of the Earth's continental crust. Examples of red granite include the famous 'Aswan Granite' used in Ancient Egyptian obelisks and the 'Texas Red' granite used in the Texas State Capitol.
Field identification & locations
Identified in the field by its interlocking mineral grains (quartz, feldspar, mica) and its hardness—it cannot be scratched by a steel knife. Common in mountainous regions or where glacial deposits have left 'erratics.'
