igneous

Granite

Phaneritic Plutonic Felsic Rock (SiO2 > 69%)

Hardness: 6-7 (Mohs scale); Color: Salt and pepper (white/pink/gray/black); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible crystals); Specific gravity: 2.63 - 2.75

Hardness: 6-7 (Mohs scale)
Color: Salt and pepper (white/pink/gray/black)
Luster: Vitreous to dull

Identified April 7, 2026More igneous →

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Physical properties

Hardness: 6-7 (Mohs scale); Color: Salt and pepper (white/pink/gray/black); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible crystals); Specific gravity: 2.63 - 2.75

Formation & geological history

Formed from the slow subterranean cooling of silica-rich magma (intrusive). They are primarily found in the continental crust and often date back millions to billions of years.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, curbing, monuments, and as crushed aggregate for infrastructure.

Geological facts

Granite is one of the hardest substances in the world, second only to diamonds. It makes up a large part of the continental crust and forms the core of many mountain ranges like the Sierra Nevada.

Field identification & locations

Identify by its interlocking 'salt and pepper' crystalline texture consisting of quartz (translucent), feldspar (opaque white/pink), and mica (black flakes); found globally in outcrop formations.

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