Igneous

Granite

Granite (Mainly Quartz, Feldspar, and Mica)

Hardness: 6-7 on Mohs scale; Color: typically white, pink, or gray with mottled dark spots; Luster: Vitreous to pearly; Crystal structure: Phaneritic (coarse-grained) crystalline texture; Cleavage: None in the mass rock, though individual mineral components like mica have perfect cleavage.

Hardness: 6-7 on Mohs scale
Color: typically white, pink, or gray with mottled dark spots
Luster: Vitreous to pearly

Identified February 15, 2026More igneous →

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Physical properties

Formation & geological history

Granite forms from the slow crystallization of magma below Earth's surface. This process occurs in batholiths and continental crust over millions of years, typically in tectonic zones. The cooling is slow enough to allow large crystals to grow.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, and memorial monuments. It is also crushed for use as aggregate in road building and ballast.

Geological facts

Granite makes up the majority of the Earth's continental crust. It is one of the hardest natural stones in the world and has been used for building since Ancient Egypt, notably in the Great Pyramid of Giza.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and interlocking crystals of roughly equal size. It will scratch glass but cannot be scratched by a steel knife. Common in mountainous regions and shield areas like the Canadian Shield or the Appalachians.

Other igneous specimens

See all

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

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral