igneous
Granite
Granite (composed primarily of Quartz SiO2, Alkali Feldspar, and Plagioclase Feldspar)
Hardness: 6-7 on Mohs scale; Color: Phaneritic (spotted) with pink, white, gray, and black minerals; Luster: Dull to vitreous; Crystal structure: Coarse-grained granular (phaneritic); Cleavage: Distinct in feldspars; Specific gravity: 2.63 - 2.75
- Hardness
- 6-7 on Mohs scale
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Phaneritic (spotted) with pink, white, gray, and black minerals; Luster: Dull to vitreous; Crystal structure: Coarse-grained granular (phaneritic); Cleavage: Distinct in feldspars; Specific gravity: 2.63 - 2.75
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface (intrusive). Geological ages vary widely from billions of years (Precambrian) to relatively recent mountain-building events.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stone, monuments, and as crushed stone for road base and concrete.
Geological facts
Granite makes up a large part of the continental crust. Because it is so hard and durable, it is the most popular choice for monuments and tombstones that must withstand weathering for centuries.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. It is found in the cores of mountain ranges and shield areas. Collectors value specimens with large accessory minerals like garnets or tourmaline.
