igneous

Granite

Plutonic Igneous Rock (composed of Quartz, Alkali Feldspar, and Plagioclase)

Hardness: 6-7 on Mohs scale; Color: Gray, white, or pink with dark specks; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained minerals visible to the naked eye); Specific gravity: 2.63 - 2.75.

Hardness: 6-7 on Mohs scale
Color: Gray, white, or pink with dark specks
Luster: Vitreous to dull

Identified February 27, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below the Earth's surface (intrusive). They can be found in continental crust across all geological ages, primarily in mountain roots or continental shields.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, and monuments. Also used as crushed stone for road base and railroad ballast.

Geological facts

Granite is the most common rock found in the Earth's continental crust. El Capitan in Yosemite National Park is one of the most famous granite monoliths in the world. It is much harder and more durable than marble.

Field identification & locations

Identify in the field by its speckled 'salt and pepper' appearance and visible interlocking crystals. It is found in large outcrops in mountain ranges. For collectors, it is a primary rock type but usually gathered as a representative sample rather than for value.

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