igneous

Granite

Granite (Felsic Plutonic Rock)

Hardness: 6-7 Mohs; Color: Salt and pepper (white/pink feldspar, gray quartz, black mica); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained coarse crystals); Cleavage: Individual minerals vary (feldspar has 2 planes at 90 degrees); Specific Gravity: 2.63 - 2.75

Hardness: 6-7 Mohs
Luster: Vitreous to dull

Identified May 19, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface (intrusive). Most continental granite dates from the Precambrian to Cenozoic eras, typically forming in continental crust above subduction zones or in mountain-building regions.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, curbing, monuments, and as aggregate for road base and concrete.

Geological facts

Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a granite batholith. It is one of the hardest and most durable materials used in human architecture.

Field identification & locations

Identify in the field by its coarse-grained interlocking crystals and lack of foliation. Common in mountain ranges and Shields (like the Canadian Shield). Look for visible specks of quartz (translucent gray) and feldspar (opaque white/pink).

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