igneous

Granite

Phaneritic Igneous Rock (composed mostly of Quartz, Feldspar, and Mica)

Hardness: 6-7 on Mohs scale; Color: Pink, white, gray, and black mottled; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarsegrained/visible crystals); Specific Gravity: 2.65-2.75

Hardness: 6-7 on Mohs scale
Color: Pink, white, gray, and black mottled
Luster: Vitreous to dull

Identified March 16, 2026More igneous →

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Physical properties

Hardness: 6-7 on Mohs scale; Color: Pink, white, gray, and black mottled; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarsegrained/visible crystals); Specific Gravity: 2.65-2.75

Formation & geological history

Formed from the slow subterranean cooling of silica-rich magma (plutonic). Found in continental crust, often dating back hundreds of millions or billions of years.

Uses & applications

Widely used in construction, countertops, monuments, curbing, and as crushed stone for road bases.

Geological facts

Granite makes up a large part of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith.

Field identification & locations

Identify by its interlocking 'salt and pepper' appearance of different colored minerals; it is extremely hard and cannot be scratched by a steel nail. Common in mountainous regions or glacial deposits.

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

Blue Apatite

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

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Magnetite

Magnetite (Fe3O4)

mineral