igneous

Granite

Granite (Phaneritic intrusive igneous rock)

Hardness: 6-7 on Mohs scale; Color: typically 'salt and pepper' (gray, white, pink, black); Luster: vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible crystals); Cleavage: none (irregular fracture); Specific gravity: 2.63 - 2.75

Hardness: 6-7 on Mohs scale
Color: typically 'salt and pepper' (gray, white, pink, black)
Luster: vitreous to dull

Identified March 20, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow crystallization of magma below the Earth's surface (plutonic). It is primarily composed of quartz, feldspar, and mica. Geological age varies greatly, but it is a major component of the continental crust.

Uses & applications

Major use in construction for countertops, floor tiles, paving stone, and curbing. Also used in monuments, sculptures, and as aggregate for road building.

Geological facts

Granite is the most common igneous rock found on Earth's continents. The iconic peaks of the Sierra Nevada mountains and Yosemite's Half Dome are composed almost entirely of granite.

Field identification & locations

Identify by its interlocking 'mosaic' of visible minerals. Search for it in mountain ranges or eroded volcanic areas. Collectors look for unique inclusions or high pink orthoclase content for aesthetic value.

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