igneous

Granite

Granite (Phaneritic Quartz-Feldspar-Biotite rock)

Hardness: 6-7 (Mohs scale), Color: Salt-and-pepper (white, gray, black), Luster: Vitreous to dull, Crystal structure: Phaneritic (visible crystals), Cleavage: None (grains have cleavage, rock fractures irregularly)

Identified May 30, 2026More igneous →

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Physical properties

Formation & geological history

Formed by the slow cooling and crystallization of magma beneath the Earth's surface (intrusive igneous). It can be billions of years old, often found in the cores of mountain ranges.

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. It is extremely durable and resistant to erosion, which is why it often forms the peaks of mountains like the Sierra Nevada.

Field identification & locations

Identify by its interlocking 'salt and pepper' crystalline texture where minerals are large enough to see with the naked eye. Commonly found in continental mountain ranges and shield areas. Excellent for beginners to practice identifying quartz, feldspar, and mica.

Other igneous specimens

See all

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

Dalmatian Jasper

Aplite with Arfvedsonite inclusions

igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Blue Apatite

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

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral