igneous

Grey Granite

Phaneritic Felsic Igneous Rock (primarily Quartz, Feldspar, and Mica)

Hardness: 6-7 (Mohs scale); Color: Salt-and-pepper grey, white, and black mottled; Luster: Dull to vitreous; Crystal Structure: Phaneritic (visible interlocking crystals); Cleavage: Indistinct in bulk, but feldspar grains show cleavage; Specific Gravity: 2.63 - 2.75

Hardness: 6-7 (Mohs scale)
Color: Salt-and-pepper grey, white, and black mottled
Luster: Dull to vitreous

Identified February 15, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below the Earth's surface (intrusive). Granite can date from the Archean Eon to the Cenozoic, typically found in continental crust and mountain ranges.

Uses & applications

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

Geological facts

Granite is the most common rock found in the Earth's continental crust. El Capitan in Yosemite National Park is one of the world's most famous granite monoliths.

Field identification & locations

Identify in the field by its coarse-grained, 'salt and pepper' appearance and extreme hardness (will readily scratch glass). Found in batholiths and mountain cores globally, such as the Appalachians or the Scottish Highlands.

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