igneous

Pink Granite (Alkali Feldspar Granite)

Phaneritic Plutonic Felsic Rock (SiO2, KAlSi3O8, NaAlSi3O8)

Hardness: 6-7 Mohs; Color: Pink, salmon, or reddish-orange due to potassium feldspar; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.63 to 2.75

Hardness: 6-7 Mohs
Color: Pink, salmon, or reddish-orange due to potassium feldspar
Luster: Vitreous to dull

Identified March 24, 2026More igneous →

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Physical properties

Hardness: 6-7 Mohs; Color: Pink, salmon, or reddish-orange due to potassium feldspar; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.63 to 2.75

Formation & geological history

Formed by the slow crystallization of silica-rich magma deep underground (plutonic). The pink hue indicates a high concentration of orthoclase (potassium feldspar). Found in continental crust from various eras, frequently dating to the Precambrian or Paleozoic.

Uses & applications

Massively used in construction for countertops, floor tiles, and monuments. It is favored for outdoor curbs and decorative landscaping due to its durability and resistance to weathering.

Geological facts

Mount Rushmore is carved into a granite batholith. The pink variety is specifically prized for architectural aesthetics. Its crystals are large enough to be seen with the naked eye because it cooled very slowly over thousands of years.

Field identification & locations

Identify by its interlocking 'salt and pepper' crystalline texture and distinct pink hue. It will scratch glass but not be scratched by a steel knife. Common in continental shields like the Canadian Shield or the Scottish Highlands.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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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

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Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral