igneous

Granite

Felsic Intrusive Igneous Rock (SiO2, Al2O3, K2O, Na2O)

Hardness: 6-7 on Mohs scale. Color: Gray, pinkish-white, and black mottled pattern. Luster: Vitreous to dull. Crystal Structure: Phaneritic (coarse-grained) featuring interlocking crystals of quartz, feldspar, and mica. Specific Gravity: 2.63 to 2.75.

Hardness: 6-7 on Mohs scale
Color: Gray, pinkish-white, and black mottled pattern
Luster: Vitreous to dull

Identified March 22, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow cooling and crystallization of silica-rich magma deep beneath the Earth's surface (plutonic). It is typically associated with continental crust and can range in age from the Precambrian to Cenozoic eras.

Uses & applications

Extensively used in construction as dimension stone, countertops, floor tiles, and as crushed aggregate for road beds and concrete. Also used for monuments and decorative architectural elements.

Geological facts

Granite makes up a significant portion of the Earth's continental crust. Because it forms at great depths, its presence at the surface indicates massive amounts of overlying rock have been eroded away over millions of years. Famous examples include the monoliths of Yosemite National Park.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and visible, interlocking crystals that are large enough to see without a lens. Often found in mountain ranges or shield areas. Collectors should look for unique mineral inclusions like garnet or tourmaline within the matrix.

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

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