igneous

Granite

Phaneritic plutonic rock (composed of quartz, alkali feldspar, and plagioclase)

Hardness 6-7 on Mohs scale; color varies from white/gray to pink/red with black specks; vitreous to dull luster; granular (phaneritic) crystal structure; poorly defined cleavage; specific gravity of 2.65-2.75.

Identified March 18, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling of silica-rich magma deep beneath the Earth's surface (plutonic) over millions of years, primarily during mountain-building events in various geological eras.

Uses & applications

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

Field identification & locations

Identify by its 'salt and pepper' appearance with visible interlocking crystals of quartz (clear/gray) and feldspar (white/pink). Found worldwide in mountain ranges and ancient continental shields. Durable and resistant to weathering.

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