igneous
Granite
Phaneritic intrusive igneous rock (composition: Quartz, Alkali Feldspar, Plagioclase Feldspar)
Hardness: 6-7 (Mohs scale); Color: Mottled pink/red, white, and gray; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible interlocking crystals); Cleavage: Indistinct; Specific Gravity: 2.63 - 2.75
- Hardness
- 6-7 (Mohs scale)
- Color
- Mottled pink/red, white, and gray
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Mottled pink/red, white, and gray; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible interlocking crystals); Cleavage: Indistinct; Specific Gravity: 2.63 - 2.75
Formation & geological history
Formed from the slow crystallization of magma below Earth's surface. This specimen shows a high concentration of potassium feldspar (orthoclase), giving it the reddish-pink hue. Ages vary globally from Precambrian to Cenozoic.
Uses & applications
Used extensively in construction for countertops, floor tiles, paving stones, and veneers; also used for monuments, sculptures, and as aggregate for roads.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Its name comes from the Latin 'granum', meaning a grain, in reference to its coarse-grained structure. It is the signature rock of the continental plates.
Field identification & locations
Identify in the field by its hard, scratch-resistant surface and visible, randomly oriented crystals of quartz (clear/gray) and feldspar (pink/white). Common in mountain ranges and glacial deposits.
