igneous

Granite

Intrusive Phaneritic Felsic Igneous Rock

Hardness: 6-7 on Mohs scale. Color: Salt and pepper appearance with shades of white, pink, grey, and black. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained) with visible crystals of quartz (clear/grey), feldspar (white/pink), and mica/amphibole (black).…

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

Identified March 26, 2026More igneous →

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Physical properties

Formation & geological history

Formed by the slow crystallization of magma below Earth's surface (plutonic). Most granite formations are millions to billions of years old (Precambrian to Cenozoic). Formed in continental crust zones.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, and monuments. Used as crushed stone for road base and concrete aggregate. Highly valued by collectors for specimens containing large garnets or tourmalines.

Geological facts

Granite makes up the bulk of Earth's continental crust. Mount Rushmore is carved into a massive granite batholith. It is one of the hardest and most durable common stones, resistant to acids and scratching.

Field identification & locations

Identify in the field by its coarse crystalline texture where grains are visible to the naked eye; it will not have layers like gneiss or small pores like basalt. Common in mountain ranges and crystalline shield areas. Collectors should look for unique mineral inclusions or large crystals.

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