Igneous

Pink Granite (Potassium-rich Granite)

Phaneritic Felsic Igneous Rock (primarily SiO2, Al2O3, K2O)

Hardness: 6-7 on Mohs scale; Color: Pink, salmon, or reddish-orange due to K-feldspar, with mottled gray quartz and black mica; Luster: Vitreous to pearly; Structure: Phaneritic (coarse-grained) crystalline; Cleavage: Two directions at 90 degrees (in feldspar crystals); Specific Gravity: 2.63-2.75

Hardness: 6-7 on Mohs scale
Luster: Vitreous to pearly

Identified March 22, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below the Earth's surface (intrusive). The pink color is caused by high concentrations of orthoclase (potassium feldspar). These rocks are typically found in continental crust and range from Precambrian to Cenozoic in age.

Uses & applications

Extensively used in construction (countertops, flooring, monuments), aggregate for road building, as a dimension stone for architecture, and occasionally as a base for sculpture due to its durability and aesthetic appeal.

Geological facts

Mount Rushmore is carved into a granite batholith. Granite is the primary rock type of the Earth's continental crust and is much less dense than the basalt found on the ocean floors. It is virtually synonymous with the stability of the continents.

Field identification & locations

Identify in the field by its visible interlocking crystals of pink feldspar, clear-to-gray glassy quartz, and dark specks of minerals like biotite or hornblende. Commonly found in batholiths and mountain belts like the Sierra Nevada 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)

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Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral