igneous

Granite

Granite (phaneritic intrusive igneous rock consisting mainly of quartz, alkali feldspar, and plagioclase)

Hardness: 6-7 Mohs; Color: Gray, salt-and-pepper, or white with black/brown flecks; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible crystals); Specific gravity: 2.65 to 2.75

Hardness: 6-7 Mohs
Color: Gray, salt-and-pepper, or white with black/brown flecks
Luster: Vitreous to dull

Identified March 24, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling of silica-rich magma deep underground (plutonic formation). Age can range from over 3.5 billion years to relatively recent geological periods, but it is a primary constituent of Earth's continental crust.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, and monuments. It is also crushed into aggregate for road building and concrete.

Geological facts

Granite makes up the core of most mountain ranges around the world, like the Sierra Nevada. It is one of the hardest natural stones and is famous for its durability, which is why it was used to build the Great Pyramid of Giza's King's Chamber.

Field identification & locations

Identify in the field by its 'salt-and-pepper' appearance and interlocking visible crystals of white/clear quartz and opaque feldspar. Commonly found in mountainous regions or as glacial erratics in plains. Collectors look for unique coloration or large inclusions.

Other igneous specimens

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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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

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Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral