igneous

Granite

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

Hardness: 6-7 on Mohs scale. Color: Mottled pink, white, and black/gray. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained). Cleavage: Varies by mineral constituent (feldspar has two directions, quartz has none). Specific gravity: 2.65 to 2.75.

Hardness: 6-7 on Mohs scale
Color: Mottled pink, white, and black/gray
Luster: Vitreous to dull

Identified March 23, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below the Earth's surface (plutonic). It is typically found in continental crust and can be billions of years old, often found in the cores of mountain ranges.

Uses & applications

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

Geological facts

Granite makes up a large portion of the Earth's continental crust. Famous landmarks like Mount Rushmore and Yosemite's Half Dome are made of granite. It is one of the hardest and most durable natural stones available.

Field identification & locations

Identify by its 'salt and pepper' appearance and visible, interlocking crystals of quartz and feldspar. It is found globally in mountainous regions and shield areas. For collectors, look for varied mineral inclusions like biotite mica or hornblende.

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