igneous

Granite

Phaneritic plutonic rock (Quartz, Alkali Feldspar, and Plagioclase)

Hardness: 6-7 on Mohs scale. Color: Mottled pink, white, and grey with black specks. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained). Cleavage: Poor; fractures along mineral boundaries. Specific gravity: 2.63 - 2.75.

Hardness: 6-7 on Mohs scale
Color: Mottled pink, white, and grey with black specks
Luster: Vitreous to dull

Identified February 16, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling and crystallization of magma deep within the Earth's crust (intrusive). Most granite dates from the Precambrian to Cenozoic eras, often associated with mountain-building events.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, and monuments due to its durability. Also used as crushed stone for road base and railroad ballast.

Geological facts

Granite makes up a large part of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in South Dakota, and the 'pink' color is usually due to an abundance of potassium feldspar.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. It is ubiquitous in continental mountain ranges. For collectors, look for unique mineral inclusions like large garnets or distinct porphyritic textures.

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