igneous

Granite

Granite (Felsic Plutonic Rock)

Hardness: 6-7 on Mohs scale. Color: Phaneritic (coarsegrained) mix of white, gray, pink, and black. Luster: Vitreous to dull. Structure: Granular, non-foliated. Composition: Primarily Quartz (SiO2), Feldspar, and Mica.

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

Identified March 23, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow crystallization of magma below Earth's surface (intrusive). Most granite dates from the Precambrian or Paleozoic eras, forming in continental crustal environments.

Uses & applications

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

Geological facts

Granite makes up a large portion of the Earth's continental crust. Mount Rushmore and Yosemite's El Capitan are famous geological formations composed entirely of granite.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. Common in mountain ranges and ancient shield areas. Collectors look for large crystals or unique color variations.

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