Igneous

Granite

Granite (Phaneritic Quartz-Feldspar intrusive rock)

Hardness: 6-7 (Mohs scale); Color: Mottled grey, white, and black; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Indistinct; Specific gravity: 2.6 – 2.7 g/cm³.

Hardness: 6-7 (Mohs scale)
Color: Mottled grey, white, and black
Luster: Dull to vitreous

Identified January 13, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface (plutonic). It is found in continental crust across all geological ages, particularly in the roots of mountain ranges.

Uses & applications

Widely used in construction for countertops, floor tiles, paving stones, and monuments due to its durability and resistance to weathering.

Geological facts

Granite makes up a large portion of the Earth's continental crust. Famous landmarks like Mount Rushmore and the base of the Statue of Liberty are made primarily of granite.

Field identification & locations

Identified in the field by its 'salt and pepper' appearance caused by interlocking crystals of quartz, feldspar, and mica. It is commonly found in batholiths and mountain cores; collectors should look for visible, interlocked mineral grains rather than layers.

Other igneous specimens

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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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

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Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral