Igneous

Granite

Granite (composed primarily of Quartz SiO2, Orthoclase KAlSi3O8, and Plagioclase NaAlSi3O8 to CaAl2Si2O8)

Hardness: 6-7 on Mohs scale; Color: Pink, white, and grey mottled; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained) crystalline; Cleavage: None (though constituent minerals like feldspar have cleavage); Specific gravity: 2.63 to 2.75.

Hardness: 6-7 on Mohs scale
Color: Pink, white, and grey mottled
Luster: Vitreous to dull

Identified March 25, 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). The pink hue indicates a high concentration of potassium feldspar. It can range in age from billions of years (Precambrian) to more recent tectonic events.

Uses & applications

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

Geological facts

Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith. It is one of the hardest and most durable natural stones available.

Field identification & locations

Identify in the field by its 'salt and pepper' or interlocking crystalline appearance where individual mineral grains (quartz, feldspar, mica) are visible to the naked eye. Found globally in mountainous regions and continental shields. Collectors value unique veining or large crystal 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

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral