igneous

Granite

Granite (Main minerals: Quartz SiO2, Feldspar KAlSi3O8, Mica)

Hardness: 6-7 on Mohs scale; Color: Grey with white and dark specks; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Perfect on feldspar grains, none on quartz grains; Specific Gravity: 2.63 - 2.75

Hardness: 6-7 on Mohs scale
Color: Grey with white and dark specks
Luster: Vitreous to dull

Identified April 6, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow crystallization of magma below the Earth's surface (intrusive). Most granite was formed during the Precambrian and Paleozoic eras in continental crust environments.

Uses & applications

Used extensively in construction for countertops, floor tiles, paving stone, monuments, and as aggregate for roads and concrete.

Geological facts

Granite makes up a large portion of the Earth's continental crust. It is extremely durable and has been used for famous monuments like Mount Rushmore and the Egyptian Pyramids.

Field identification & locations

Identify in the field by its speckled 'salt and pepper' appearance and visible interlocking crystals. It is found worldwide in mountainous regions and areas where ancient root belts are exposed.

Other igneous specimens

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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