igneous

Granite

Granite (Phaneritic intrusion / SiO2 + KAlSi3O8 + NaAlSi3O8)

Hardness: 6-7 Mohs; Color: Gray, salt-and-pepper, or white mottled with black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible crystals); Specific gravity: 2.63 to 2.75.

Hardness: 6-7 Mohs
Color: Gray, salt-and-pepper, or white mottled with black
Luster: Vitreous to dull

Identified February 21, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface (plutonic). It is primarily composed of quartz, feldspar, and mica. Geological age ranges from the Archean Eon to the Cenozoic Era depending on location.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, curbing, and monuments. It is also a source for dimension stone and crushed stone aggregate.

Geological facts

Granite makes up a large portion of the Earth's continental crust. El Capitan in Yosemite National Park is one of the most famous exposed granite monoliths in the world. It is highly resistant to acid rain and weathering.

Field identification & locations

Identify by its interlocking 'salt-and-pepper' appearance where quartz and feldspar grain boundaries are easily visible to the naked eye. Common across continental shields and mountain ranges. Collectors look for unique large-crystal varieties like pegmatites.

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