igneous
Granitoid (Granitic Rock)
Granitoid (Quartzo-feldspathic plutonic rock)
Hardness: 6-7 on Mohs scale; Color: Salt and pepper appearance with shades of white, gray, and tan; Luster: Dull to vitreous (on crystal faces); Crystal structure: Phaneritic (visible interlocking grains); Composition: Primarily quartz, feldspar, and minor biotite/hornblende.
- Hardness
- 6-7 on Mohs scale
- Luster
- Dull to vitreous (on crystal faces)
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Salt and pepper appearance with shades of white, gray, and tan; Luster: Dull to vitreous (on crystal faces); Crystal structure: Phaneritic (visible interlocking grains); Composition: Primarily quartz, feldspar, and minor biotite/hornblende.
Formation & geological history
Formed through the slow cooling and crystallization of silica-rich magma deep within the Earth's crust (plutonic formation). These rocks typically date from the Precambrian to Cenozoic eras.
Uses & applications
Used widely in construction (crushed stone, aggregate) and as dimension stone for countertops and monuments. Also valuable for studying crustal evolution.
Geological facts
Granite is the most common rock found in the continental crust and forms the core of many mountain ranges. Large crystals indicate the magma cooled extremely slowly over thousands of years.
Field identification & locations
Identify in the field by its interlocking 'crystalline' texture and lack of layering (foliation). It is extremely common in shield areas like the Canadian Shield or Appalachian region.
