igneous

Granite

Granite (Felsic Plutonic Rock)

Hardness: 6-7 Mohs; Color: Speckled gray, pink, and white; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained); Cleavage: Irregular/None; Specific gravity: 2.63 - 2.75

Hardness: 6-7 Mohs
Color: Speckled gray, pink, and white
Luster: Dull to vitreous

Identified March 22, 2026More igneous →

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Physical properties

Hardness: 6-7 Mohs; Color: Speckled gray, pink, and white; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained); Cleavage: Irregular/None; Specific gravity: 2.63 - 2.75

Formation & geological history

Formed from the slow cooling and solidification of magma deep within the Earth's crust (plutonic). Found in continental crust, often appearing in mountain ranges after millions of years of erosion.

Uses & applications

Extensively used in construction, flooring, kitchen countertops, monuments, and as aggregate for roads and railroads due to its durability.

Geological facts

Granite is one of the hardest substances in the world. Famous structures like Mount Rushmore are carved from granite. It is an 'intrusive' rock, meaning it cooled underground.

Field identification & locations

Identify by its interlocking 'salt and pepper' crystalline texture and the presence of visible quartz (glassy) and feldspar (blocky). Commonly found in cratons and mountain cores like the Sierra Nevada or the Appalachians.

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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