igneous

Granite

Phaneritic Intrusive Igneous Rock (composed primarily of Quartz, Feldspar, and Mica)

Hardness: 6-7 (Mohs scale); Color: Salt and pepper (white/gray with black specks); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Distinct in feldspar grains, none in quartz; Specific gravity: 2.63 - 2.75

Hardness: 6-7 (Mohs scale)
Color: Salt and pepper (white/gray with black specks)
Luster: Vitreous to dull

Identified March 11, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface. Granite is part of the continental crust and can date back billions of years (Archean Eon) to more recent tectonic events. It forms in plutons or batholiths deep underground.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stone, curbing, and monuments. It is also a popular aggregate for road construction and a staple for teaching basic geology and mineral identification.

Geological facts

Granite makes up a large portion of the Earth's continental crust. Its name comes from the Latin 'granum', meaning a grain, referring to its coarse-grained texture. Famous landmarks like Mount Rushmore and Yosemite's Half Dome are composed of granite.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and large, interlocked mineral grains. Look for translucent quartz, opaque white or pink feldspar, and shiny black biotite or hornblende. It is ubiquitous in mountainous regions and glacial deposits.

Other igneous specimens

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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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)

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Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral