igneous

Granite

Phaneritic Igneous Rock (composed primarily of Quartz SiO2, Alkali Feldspar (K,Na)AlSi3O8, and Plagioclase Feldspar)

Hardness: 6-7 on Mohs scale; Color: Pinkish-tan with dark inclusions; Luster: Vitreous to dull; Crystal structure: Phaneritic (visible coarse-grained crystals); Cleavage: Perfect in two directions for feldspar components.

Hardness: 6-7 on Mohs scale
Color: Pinkish-tan with dark inclusions
Luster: Vitreous to dull

Identified March 20, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface (intrusive). This process occurrs over millions of years within the Earth's crust, commonly associated with continental plates.

Uses & applications

Widely used as a construction material for countertops, floor tiles, paving stone, and curbing. It is also used in monument carving and as high-quality aggregate for road building.

Geological facts

Granite makes up a large part of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith. Its name comes from the Latin 'granum', meaning a grain, in reference to its coarse-grained structure.

Field identification & locations

Identify in the field by its 'salt and pepper' or multicrystalline appearance where individual mineral grains (pink feldspar, clear quartz, dark mica/hornblende) are large enough to see with the naked eye. Found globally in mountainous regions and shield areas.

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