igneous
Red Granite
Phaneritic plutonic rock (High-potassium feldspar granite)
Hardness: 6-7 Mohs; Color: Pinkish-red to deep red, mottled with black and grey; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained); Cleavage: Indistinct; Specific gravity: 2.63 to 2.75
- Hardness
- 6-7 Mohs
- Color
- Pinkish-red to deep red, mottled with black and grey
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Pinkish-red to deep red, mottled with black and grey; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained); Cleavage: Indistinct; Specific gravity: 2.63 to 2.75
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground (plutonic). The red color is caused by an abundance of potassium feldspar (orthoclase) containing trace heralds of hematite or iron oxide.
Uses & applications
Used extensively in construction for countertops, floor tiles, and monuments. Red varieties are particularly popular for decorative landscaping and gravestones due to their vibrant color and durability.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Famous locations for stunning red granite include the Aswan quarries in Egypt (used for ancient obelisks) and the Llano Uplift in Texas.
Field identification & locations
Identify in the field by its coarse crystalline texture (grains visible to the naked eye) and lack of foliation. Look for the interlocking 'salt and pepper' appearance of quartz, feldspar, and biotite. Found in mountainous regions or where ancient tectonic movement has exposed deep-seated batholiths.
