igneous

Granite

Phaneritic plutonic rock (composed of Quartz, Feldspar, and Mica/Amphibole)

Hardness: 6-7 on Mohs scale; Color: Salt-and-pepper (mottled grey, white, and black); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Dependent on mineral (feldspar has two planes, quartz has none); Specific gravity: 2.63 - 2.75

Hardness: 6-7 on Mohs scale
Color: Salt-and-pepper (mottled grey, white, and black)
Luster: Vitreous to dull

Identified March 1, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling and solidification of silica-rich magma deep underground (plutonic). Found in continental crust, often dating back to various orogenic (mountain-building) events across geological time.

Uses & applications

Extensively used in construction as dimension stone, countertops, floor tiles, and as crushed stone for road base or railway ballast. Its durability and aesthetic appeal also make it popular for monuments and sculptures.

Geological facts

Granite makes up a large portion of the Earth's continental crust and is unique to Earth among the planets in our solar system. The famous peaks in Yosemite National Park and the faces on Mount Rushmore are carved from granite.

Field identification & locations

Identify in the field by its interlocking, visible 'speckled' crystals that are uniform throughout the rock rather than in layers. It is ubiquitous in mountainous regions and shield areas like the Canadian Shield or the Appalachians. Collectors look for 'pegmatites' where the crystal sizes are exceptionally large.

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