igneous

Granite

Granite (Felsic Plutonic Rock)

Hardness: 6-7 on Mohs scale. Color: Spotted or speckled mix of tan, gray, and black. Luster: Vitreous to dull. Crystal Structure: Phaneritic (coarse-grained). Cleavage: Varies by mineral content. Specific Gravity: 2.65 to 2.75.

Hardness: 6-7 on Mohs scale
Color: Spotted or speckled mix of tan, gray, and black
Luster: Vitreous to dull

Identified April 10, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface (intrusive). They can be hundreds of millions to billions of years old, often found in the continental crust.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, curbing, and monuments because of its durability and aesthetic appeal.

Geological facts

Granite makes up a large part of the Earth's continental crust. It is one of the hardest substances in the world, second only to diamonds. Famous landmarks like Mount Rushmore are carved from granite.

Field identification & locations

Identify in the field by its interlocking coarse grains of quartz, feldspar, and mica. It is ubiquitous in mountainous regions and shield areas like the Canadian Shield or the Appalachians.

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