igneous

Granite

Intrusive Felsic Igneous Rock

Hardness: 6-7 on the Mohs scale; Color: Gray, light-pink, or white; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Indistinct; Specific gravity: 2.63 to 2.75

Hardness: 6-7 on the Mohs scale
Color: Gray, light-pink, or white
Luster: Dull to vitreous

Identified March 19, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface. It is primarily composed of quartz and feldspar with minor amounts of mica and amphiboles. Most granite dates back to the Precambrian or Paleozoic eras.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, curbing, and monuments. Due to its durability, it is also used in structural engineering and architectural facades.

Geological facts

Granite makes up a large portion of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith in South Dakota. It is one of the hardest and most durable common stones available.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking mineral crystals. It is found in mountain ranges and continental shield areas globally. Collectors should look for unique mineral inclusions like tourmaline or garnet.

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