igneous

Granite

Granite (Silicic Plutonic Rock)

Hardness: 6-7 on Mohs scale; Color: Phaneritic texture with pink (potassium feldspar), white (plagioclase), gray (quartz), and black (biotite/hornblende); Luster: Vitreous to dull; Crystal structure: Granular/crystalline; Cleavage: None (though feldspars within it have cleavage); Specific gravity: 2.63 to 2.75

Hardness: 6-7 on Mohs scale
Luster: Vitreous to dull

Identified March 29, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface (intrusive). Most granite dates from the Precambrian to Cenozoic eras, typically found in continental crust within mountain belts and cratons.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stone, and curbing. It is also used for dimensional stone in monuments and as crushed stone for road base.

Geological facts

Granite makes up a large portion of the Earth's continental crust. It is the signature rock of the planet Earth, as it is not found in significant quantities on other planets or the moon.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. It is found globally in mountainous regions and areas where ancient crust is exposed. For collectors, look for specimens with large 'phenocrysts' or unique colors.

Other igneous specimens

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous