igneous

Granite

Granite (Felsic Plutonic Rock)

Hardness: 6-7 Mohs; Color: Speckled salt-and-pepper look with pink, white, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Indistinct; Specific gravity: 2.63 to 2.75

Hardness: 6-7 Mohs
Color: Speckled salt-and-pepper look with pink, white, and black
Luster: Vitreous to dull

Identified March 17, 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 forming in continental crust above subduction zones or in mountain-building regions.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, and memorial monuments due to its durability and resistance to weathering.

Geological facts

Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in South Dakota. It contains natural traces of uranium and can emit small amounts of radon gas.

Field identification & locations

Identify by its interlocking 'salt and pepper' grains of quartz (clear/gray), feldspar (white/pink), and mica (black/shiny). Found globally in continental shields. For collectors, look for specimens with large crystals or unique color variations.

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