igneous

Granite

Phaneritic Igneous Rock (composed of quartz, alkali feldspar, and plagioclase)

Hardness: 6-7 on Mohs scale; Color: Pink, white, gray, and black speckled appearance; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Indistinct; Specific gravity: 2.63 to 2.75

Hardness: 6-7 on Mohs scale
Color: Pink, white, gray, and black speckled appearance
Luster: Vitreous to dull

Identified March 28, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow crystallization of magma below Earth's surface (intrusive). It is found in continental crust and is common in mountain ranges and ancient shield areas, ranging from billions of years old to relatively recent geological timeframes.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, curbing, and monuments. It is also crushed into aggregate for 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 composed of granite. It is one of the hardest and most durable natural stones available.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. It is ubiquitous in mountainous terrains and gravel pits. Collectors look for unique colorations or large feldspar phenocrysts (porphyritic granite).

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