igneous

Granite

Plutonic Granite

Hardness: 6-7 on Mohs scale; Color: Pink, white, gray, and black mottled; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: None (minerals within have individual cleavage); Specific gravity: 2.63 to 2.75

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

Identified May 27, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow crystallization of magma below Earth's surface. It is a coarse-grained intrusive rock that can date back billions of years, often forming the core of continental tectonic plates.

Uses & applications

Widely used in construction for countertops, flooring, curbing, and monuments. Also used as crushed stone for road base and aggregate.

Geological facts

Granite makes up a large part of the continental crust. Mount Rushmore is carved into a granite batholith. It is one of the hardest and most durable natural stones available.

Field identification & locations

Identify in the field by its visible interlocking crystals of quartz (clear/gray), feldspar (pink/white), and mica (black/shiny). Common in mountain ranges and glacial deposits.

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