igneous
Granite
Phaneritic Igneous Rock (Granite)
Hardness: 6-7 on Mohs scale. Color: Pink (orthoclase feldspar), white (plagioclase), gray (quartz), and black (amphibole or biotite). Luster: Vitreous to dull. Structure: Phaneritic (coarse-grained) crystalline. Cleavage: Indistinct on the rock itself but present in mineral components. Specific Gravity: 2.63 to 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: Pink (orthoclase feldspar), white (plagioclase), gray (quartz), and black (amphibole or biotite). Luster: Vitreous to dull. Structure: Phaneritic (coarse-grained) crystalline. Cleavage: Indistinct on the rock itself but present in mineral components. Specific Gravity: 2.63 to 2.75.
Formation & geological history
Formed through the slow crystallization of magma below Earth's surface (intrusive). Most granite dates from the Precambrian or Paleozoic eras, found in continental crust within batholiths.
Uses & applications
Major use in construction as dimension stone, kitchen countertops, flooring, and road base material. Also used for monuments, sculptures, and as aggregate for concrete.
Geological facts
Granite makes up a large portion of the Earth's continental crust. It is extremely durable and resistant to erosion, which is why it forms the core of many mountain ranges.
Field identification & locations
Identify by its interlocking texture of multicolored minerals and its hardness (it will not be scratched by a steel knife). Commonly found in mountainous regions or glacial till where it has been transported. Collectors look for unique color patterns and grain sizes.
