igneous

Granite

Phaneritic plutonic rock (composed mainly of SiO2, Al2O3, K2O, and Na2O)

Hardness: 6-7 on Mohs scale; Color: Mottled gray, white, and pinkish-tan; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained) equigranular crystals; Cleavage: None (fractures irregularly); Specific gravity: 2.63 to 2.75

Hardness: 6-7 on Mohs scale
Color: Mottled gray, white, and pinkish-tan
Luster: Vitreous to dull

Identified March 18, 2026More igneous →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed by the slow crystallization of magma below Earth's surface (intrusive). Typical age ranges from Precambrian to Cenozoic. It forms the core of most continental crustal masses.

Uses & applications

Used extensively in construction for countertops, floor tiles, paving stones, and curbing. It is also used for cemetery monuments, bridges, and as crushed stone for road base.

Geological facts

Granite is the most common igneous rock found on Earth's surface. Mount Rushmore in South Dakota is carved directly into a granite batholith. It often contains trace amounts of uranium, which is why some granite countertops can emit small amounts of radon gas.

Field identification & locations

Identify by its interlocking 'salt and pepper' appearance with visible crystals of quartz (clear/gray), feldspar (white/pink), and mica (black/shiny). Found in mountainous regions and glacial deposits. Collector interest is generally for polished slabs or specific mineral inclusions.

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

Blue Apatite

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

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Magnetite

Magnetite (Fe3O4)

mineral