igneous

Granite

Granite (Felsic Plutonic Rock)

Hardness: 6-7 on Mohs scale; Color: Mottled pink, white, gray, and black; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained) with visible crystals of quartz, feldspar, and mica; Cleavage: Depends on individual mineral grains; Specific gravity: 2.63 - 2.75.

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

Identified March 13, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below the Earth's surface. It is a plutonic rock that forms deep within the crust over millions of years, often associated with continental crust formation and mountain-building events (Orogeny).

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, and memorial monuments. It is also used as crushed stone in road base and aggregate for concrete.

Geological facts

Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith. It is one of the hardest and most durable natural stones, making it a preferred choice for high-traffic surfaces.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and large visible crystals. It lacks any layering or banding (unlike gneiss). Commonly found in mountainous regions or where ancient tectonic plates have collided, such as the Canadian Shield, the Appalachians, or Dartmoor, UK.

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