Igneous

Granite

Granite (Felsic Plutonic Rock)

Hardness: 6-7 on Mohs scale; Color: typically mottled pink, white, gray, and black; Luster: Vitreous to pearly; Crystal structure: Phaneritic (coarse-grained); Cleavage: None (the constituent minerals like feldspar have cleavage, but the rock itself breaks irregularly).

Hardness: 6-7 on Mohs scale
Color: typically mottled pink, white, gray, and black
Luster: Vitreous to pearly

Identified March 16, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow crystallization of magma below Earth's surface (intrusive). It is a major component of the continental crust, with examples ranging from hundreds of millions to billions of years old.

Uses & applications

Extensively used in construction (countertops, floor tiles, paving stones), monuments, curbing, and as crushed stone for road base and railroad ballast.

Geological facts

Granite makes up the majority of the Earth's continental crust. Famous natural formations include Yosemite's Half Dome and Mount Rushmore, where the presidential faces are carved into a granite batholith.

Field identification & locations

Identify in the field by its coarse 'salt and pepper' appearance and visible interlocking crystals of quartz, feldspar, and mica. It is found in abundance in mountain ranges and ancient 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