igneous

Granite

Granite (composed primarily of Quartz SiO2, Alkali Feldspar, and Plagioclase Feldspar)

Hardness: 6-7 on Mohs scale; Color: Phaneritic (spotted) with pink, white, gray, and black minerals; Luster: Dull to vitreous; Crystal structure: Coarse-grained granular (phaneritic); Cleavage: Distinct in feldspars; Specific gravity: 2.63 - 2.75

Hardness: 6-7 on Mohs scale
Luster: Dull to vitreous

Identified March 14, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface (intrusive). Geological ages vary widely from billions of years (Precambrian) to relatively recent mountain-building events.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stone, monuments, and as crushed stone for road base and concrete.

Geological facts

Granite makes up a large part of the continental crust. Because it is so hard and durable, it is the most popular choice for monuments and tombstones that must withstand weathering for centuries.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. It is found in the cores of mountain ranges and shield areas. Collectors value specimens with large accessory minerals like garnets or tourmaline.

Other igneous specimens

See all

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