igneous

Granite

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

Hardness: 6-7 on Mohs scale; Color: Pink, white, gray, and black speckles; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible coarse grains); Cleavage: Dependent on mineral (Feldspar has good cleavage, Quartz has none); Specific gravity: 2.63 to 2.75

Hardness: 6-7 on Mohs scale
Color: Pink, white, gray, and black speckles
Luster: Vitreous to dull

Identified March 16, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface (intrusive). They can range in age from billions of years old to relatively young, found typically in continental crust mountainous regions.

Uses & applications

Used extensively in construction for countertops, floor tiles, paving stones, curbing, and monuments. Also popular as a crushed stone for road base and railroad ballast.

Geological facts

Granite makes up a large portion of the Earth's continental crust. Famous landmarks made of granite include Mount Rushmore and the base of the Statue of Liberty.

Field identification & locations

Identify by its 'salt and pepper' appearance and visible interlocking crystals. It is found globally in large plutons or batholiths. Collectors look for large crystals or unusual mineral inclusions like tourmaline or garnet.

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