igneous

Granite

Plutonic Igneous Rock (composed primarily of Quartz, Feldspar, and Mica)

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

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

Identified February 21, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow crystallization of magma below Earth's surface. High in silica and alkali metals, these intrusive rocks cool over thousands of years to create large visible crystals. Found throughout Earth's crust across all geological ages.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, and memorial monuments. Industrial uses include use as an aggregate in concrete and railroad ballast.

Geological facts

Granite makes up a large part of the continental crust. Half Dome in Yosemite National Park is one of the world's most famous granite monoliths. It is one of the hardest and most durable rocks common on the surface.

Field identification & locations

Identify by its 'salt and pepper' appearance and visible interlocking crystals. It is ubiquitous in mountainous regions and areas with exposed bedrock. Collectors look for unique mineral inclusions like tourmaline or garnets.

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