igneous

Granite

Phaneritic Plutonic Felsic Rock (SiO2, KAlSi3O8, NaAlSi3O8, CaAl2Si2O8)

Hardness: 6-7 on Mohs scale; Color: Salt and pepper/mottled white, grey, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Indistinct; Specific gravity: 2.65-2.75.

Hardness: 6-7 on Mohs scale
Color: Salt and pepper/mottled white, grey, and black
Luster: Vitreous to dull

Identified April 10, 2026More igneous →

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Physical properties

Formation & geological history

Formed by the slow crystallization of magma below the Earth's surface in continental crust. These intrusive plutons can range from billions of years old to relatively young in geological terms.

Uses & applications

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

Geological facts

Granite makes up a large portion of the Earth's continental crust. Because it is so hard and dense, it can be polished to a mirror finish, a property valued in architecture.

Field identification & locations

Identify in the field by looking for a coarse-grained, interlocking texture of light-colored minerals (quartz/feldspar) and dark minerals (biotite/hornblende). It is found worldwide in mountainous or cratonic regions.

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