igneous

Granite

Granite (phaneritic intrusive igneous rock consisting of 20-60% quartz, orthoclase/plagioclase feldspar, and mica/amphibole)

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

Hardness: 6-7 on Mohs scale
Color: Pink, gray, white with black specks
Luster: Vitreous to dull

Identified March 24, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of silica-rich magma below Earth's surface. It can date from almost any geological age, though most prevalent in the Precambrian. Found in continental crust and mountain ranges.

Uses & applications

Major use in construction as dimension stone, monuments, gravel/aggregate, countertops, and floor tiles. High-quality colored variants are used in ornamental carving.

Geological facts

Granite makes up the majority of the Earth's continental crust. Because it is so hard, it allows mountains like the Himalayas and the Alps to reach their extreme heights without collapsing under their own weight.

Field identification & locations

Identify by its 'salt and pepper' appearance and large interlocking crystals of quartz and feldspar. Found globally in batholiths and mountain cores. Field collectors should look for its inability to be scratched by a steel blade.

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