igneous

Granite

Granite (composed primarily of Quartz SiO2, Feldspar (KAlSi3O8), and Mica)

Hardness: 6-7 on Mohs scale; Color: Phaneritic (visible grains) of salt-and-pepper white, grey, and pink; Luster: Vitreous to dull; Crystal structure: Massive/granular; Specific Gravity: 2.63 to 2.75.

Hardness: 6-7 on Mohs scale
Luster: Vitreous to dull

Identified March 18, 2026More igneous →

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Physical properties

Formation & geological history

Formed by the slow crystallization of magma below Earth's surface (intrusive). The large mineral grains indicate a cooling process spanning thousands to millions of years, typically within continental crust orogenic belts.

Uses & applications

Extensively used as a dimension stone in construction for countertops, floor tiles, and paving. Highly valued in industry as crushed stone for road aggregate and railroad ballast due to its durability.

Geological facts

Granite makes up much of the Earth's continental crust. Famous landmarks like Mount Rushmore and the Egyptian Pyramids (interior chambers) are carved from granite. It is one of the hardest natural stones available.

Field identification & locations

Identify in the field by its coarse-grained texture where individual crystals of quartz (glassy) and feldspar (blocky) are visible. Commonly found in mountain ranges and continental shields. Collectors should look for 'pegmatite' varieties for larger crystals.

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