igneous

Granite

Granite (composed primarily of Quartz SiO2, Feldspar (KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8), and Mica)

Hardness: 6-7 on Mohs scale; Color: White, gray, pink, and black salt-and-pepper look; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Individual minerals have cleavage, but the rock has none; Specific gravity: 2.63 to 2.75

Hardness: 6-7 on Mohs scale
Color: White, gray, pink, and black salt-and-pepper look
Luster: Vitreous to dull

Identified June 3, 2026More igneous →

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Physical properties

Formation & geological history

Formed by the slow crystallization of magma below Earth's surface (intrusive). Found in continental crust and mountain ranges, often dating back to the Precambrian or Paleozoic eras.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stone, monuments, and as crushed stone for road base.

Geological facts

Granite is the most common rock found on the Earth's continental surface. Mount Rushmore is carved into a massive granite batholith in South Dakota.

Field identification & locations

Identify in the field by its interlocking coarse crystals and 'salt and pepper' appearance. Common in mountainous regions like the Sierra Nevada or the Appalachians. Collectors look for large crystals or unique coloration.

Other igneous specimens

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Granite

Igneous

Granite

Igneous

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dalmatian Jasper

Aplite with Arfvedsonite inclusions

igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

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