igneous
Granite
Granite (composed primarily of Quartz (SiO2), Alkali Feldspar, and Plagioclase)
Hardness: 6-7 on Mohs scale; Color: Phaneritic texture (salt and pepper appearance) with white/grey quartz, white/pink feldspar, and black biotite/hornblende speckles; Luster: Vitreous to dull; Structure: Massive, granular crystalline; Cleavage: Poor; Specific Gravity: 2.63 - 2.75.
- Hardness
- 6-7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Phaneritic texture (salt and pepper appearance) with white/grey quartz, white/pink feldspar, and black biotite/hornblende speckles; Luster: Vitreous to dull; Structure: Massive, granular crystalline; Cleavage: Poor; Specific Gravity: 2.63 - 2.75.
Formation & geological history
Formed through the slow crystallization of magma below the Earth's surface (intrusive). The large grain size indicates a cooling process that took millions of years. It can date from the Archean Eon to the Cenozoic Era depending on the specific location.
Uses & applications
Extensively used in construction for countertops, floor tiles, paving stones, and monuments (like Mount Rushmore). Historically used for building many of the world's ancient pyramids and temples. Also used as crushed stone for road base.
Geological facts
Granite makes up a large portion of the Earth's continental crust. Unlike oceanic crust (basalt), granite is less dense, which is why the continents 'float' higher on the mantle. The word comes from the Latin 'granum,' meaning a grain.
Field identification & locations
Identify in the field by its coarse-grained interlocking crystals and lack of foliation (layers). It is found in mountain ranges and continental shields globally, such as the Sierra Nevada (USA) or the Scottish Highlands. For collectors, look for specimens with large, well-defined crystals or unique colors.
