igneous
Granite
Intrusive Felsic Igneous Rock (composed mainly of Quartz, Plagioclase, Alkali Feldspar, Biotite, and Amphibole)
Hardness: 6-7 on the Mohs scale. Color: Mottled salt-and-pepper white, grey, and black. Luster: Vitreous to dull depending on weathering. Structure: Phaneritic (coarse-grained coarse-crystalline texture). Cleavage: Varies by component minerals (feldspar shows blocky cleavage). Specific Gravity: ~2.65 - 2.75.
- Hardness
- 6-7 on the Mohs scale
- Color
- Mottled salt-and-pepper white, grey, and black
- Luster
- Vitreous to dull depending on weathering
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Physical properties
Hardness: 6-7 on the Mohs scale. Color: Mottled salt-and-pepper white, grey, and black. Luster: Vitreous to dull depending on weathering. Structure: Phaneritic (coarse-grained coarse-crystalline texture). Cleavage: Varies by component minerals (feldspar shows blocky cleavage). Specific Gravity: ~2.65 - 2.75.
Formation & geological history
Formed by the slow crystallization of felsic magma beneath the Earth's surface at deep crustal levels. Over time, erosion and uplift bring these plutonic formations to the surface, where stream or river action can round them into smooth pebbles and cobbles.
Uses & applications
Extensively used in construction, stone countertops, monument carving, road aggregate, architectural facades, and land stabilization. Stream-rounded cobbles are popular in landscaping and decorative gardens.
Geological facts
Granite makes up a large portion of the Earth's continental crust. It is exceptionally durable, weather-resistant, and can withstand significant pressure, making it one of humanity's most historically important building materials, used from ancient Egyptian obelisks to modern skyscrapers.
Field identification & locations
Identified in the field by its distinct salt-and-pepper speckled pattern with coarse, visible interlocking grains of whitish/grey feldspar, glassy quartz, and dark biotite or hornblende. Commonly found along riverbeds, beaches, glacial deposits, and mountain streams worldwide.
