igneous

Granite

Plutonic Igneous Rock (composed primarily of Quartz, Alkali Feldspar, and Plagioclase)

Hardness: 6-7 on Mohs scale; Color: typically white, pink, or gray with dark speckles; Luster: vitreous to pearly; Crystal structure: phaneritic (coarsegrained) with interlocking crystals; Cleavage: imperfect; Specific gravity: 2.63 to 2.75

Hardness: 6-7 on Mohs scale
Color: typically white, pink, or gray with dark speckles
Luster: vitreous to pearly

Identified March 27, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface. It can be found in formations dating back millions or billions of years, often as part of continental crust or mountain ranges.

Uses & applications

Extensively used in construction for countertops, floor tiles, and paving stones. It is also used for monuments, sculptures, and occasionally as a crushed stone for road bases.

Geological facts

Granite is one of the hardest and most durable rocks on Earth. Its name comes from the Latin 'granum', meaning a grain, in reference to its coarse-grained structure. Mount Rushmore is carved from a granite batholith.

Field identification & locations

Identify in the field by its massive, unlayered structure and visible salt-and-pepper crystalline texture. Common in the core of mountain ranges like the Sierra Nevada or the Appalachians. Collectors look for large crystals or rare color variations.

Other igneous specimens

See all

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

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral