igneous
Granite
Phaneritic Plutonic Rock (Granite)
Hardness: 6-7 (Mohs scale); Color: Mottle of gray, white, black, and pink; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained crystals visible to the naked eye); Cleavage: Indistinct; Specific gravity: 2.63 - 2.75.
- Hardness
- 6-7 (Mohs scale)
- Color
- Mottle of gray, white, black, and pink
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Mottle of gray, white, black, and pink; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained crystals visible to the naked eye); Cleavage: Indistinct; Specific gravity: 2.63 - 2.75.
Formation & geological history
Granite forms from the slow crystallization of magma below Earth's surface. It is a plutonic intrusive rock, often forming large masses called batholiths. It usually dates from millions to billions of years old across various geological eras.
Uses & applications
Extensively used in construction (countertops, floor tiles, paving stones), as dimensional stone in monuments/statues, and as crushed stone for road base and railroad ballast.
Geological facts
Granite is the primary rock making up the Earth's continental crust. It is highly resistant to acid rain and mechanical wear, which is why it has been used for thousands of years, notably by the Ancient Egyptians for temples and sarcophagi.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible crystals of quartz, feldspar, and mica. It is found in mountain ranges and Shields (like the Canadian Shield). Collectors should look for large interlocking crystals of minerals like pink Potassium Feldspar or shiny Muscovite/Biotite.
