igneous

Granite

Phaneritic intrusive igneous rock (approx. 70 percent SiO2)

Hardness: 6-7 Mohs; Color: Salt and pepper/mottled pink, white, gray, black; Luster: Vitreous to pearly; Structure: Phaneritic (coarse-grained) crystals; Cleavage: None in the bulk rock, but present in individual mineral grains; Specific Gravity: 2.65-2.75.

Hardness: 6-7 Mohs
Color: Salt and pepper/mottled pink, white, gray, black
Luster: Vitreous to pearly

Identified May 23, 2026More igneous →

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Physical properties

Formation & geological history

Formed by the slow crystallization of silica-rich magma beneath the Earth's surface over millions of years. This specimen shows a phaneritic texture characteristic of plutonic environments where slow cooling allows large crystals to grow.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, and monuments. Also used as crushed stone for road base and concrete aggregate. High-quality specimens are collected for geological study.

Geological facts

Granite makes up much of the continuous continental crust. It is primarily composed of quartz, feldspar, and mica. The famous faces of Mount Rushmore are carved into a granite batholith.

Field identification & locations

Identify in the field by its visible interlocking crystals of quartz (clear/gray), feldspar (white/pink), and dark minerals like biotite or hornblende. It is found in large mountain ranges and shield areas globally.

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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)

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Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

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

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Magnetite

Magnetite (Fe3O4)

mineral