igneous

Granite

Phaneritic Felsic Igneous Rock (Main minerals: SiO2, KAlSi3O8, NaAlSi3O8)

Hardness: 6-7 Mohs; Color: Salt and pepper/mottled grey, tan, and white; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Specific gravity: 2.63 - 2.75.

Hardness: 6-7 Mohs
Color: Salt and pepper/mottled grey, tan, and white
Luster: Vitreous to dull

Identified April 7, 2026More igneous →

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Physical properties

Hardness: 6-7 Mohs; Color: Salt and pepper/mottled grey, tan, and white; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Specific gravity: 2.63 - 2.75.

Formation & geological history

Formed by the slow crystallization of magma below Earth's surface (intrusive). Most granite dates to various eras throughout the Precambrian, Paleozoic, and Mesozoic, forming in continental crustal environments.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, curbing, and monuments due to its durability and aesthetic appeal.

Geological facts

Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a granite batholith, and the rock is known for being extremely resistant to weathering.

Field identification & locations

Identify in the field by its light color and interlocking, multi-colored mineral grains (quartz, feldspar, and mica) that 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