igneous

Granite

Granite (Felsic Plutonic Rock / SiO2 + Al2O3)

Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (white, pink, gray, and black). Luster: Vitreous to dull. Structure: Phaneritic (coarse-grained) crystalline. Specific gravity: 2.63 to 2.75.

Hardness: 6-7 on Mohs scale
Color: Salt-and-pepper (white, pink, gray, and black)
Luster: Vitreous to dull

Identified January 12, 2026More igneous →

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Physical properties

Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (white, pink, gray, and black). Luster: Vitreous to dull. Structure: Phaneritic (coarse-grained) crystalline. Specific gravity: 2.63 to 2.75.

Formation & geological history

Formed through the slow crystallization of magma below the Earth's surface (intrusive). They can range from Archean to Cenozoic ages and are primarily found in the continental crust (batholiths and plutons).

Uses & applications

Used extensively in construction for countertops, floor tiles, paving stones, and monuments. It is also used as crushed stone (aggregate) for road building and concrete.

Geological facts

Granite is actually harder than marble and is one of the most common rocks 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 visible interlocking crystals of quartz (clear/gray), feldspar (white/pink), and mica (black/shiny). Common in mountain ranges and shield areas. It will not react with acid, unlike limestone.

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