igneous

Granite (Micro-specimen)

Plutonic Igneous Rock (primarily Quartz, Feldspar, and Mica)

Hardness: 6-7 on Mohs scale; Color: Salt-and-pepper (white, grey, and black); Luster: Vitreous to pearly; Crystal structure: Phaneritic (coarse-grained); Cleavage: Dependent on mineral inclusions; Specific gravity: 2.63 to 2.75.

Hardness: 6-7 on Mohs scale
Color: Salt-and-pepper (white, grey, and black)
Luster: Vitreous to pearly

Identified February 14, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow crystallization of magma below Earth's surface. These rocks are found in continental crust and can range from Precambrian to relatively recent geological ages.

Uses & applications

Extensively used in construction (countertops, flooring, monuments) and as crushed stone for road base. Smaller specimens are used for educational geological kits.

Geological facts

Granite makes up the majority of the Earth's continental crust. Mount Rushmore is carved into a massive granite batholith.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. Found globally in mountainous regions and shield areas. Collectors look for large, well-defined crystals.

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

Blue Apatite

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

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Magnetite

Magnetite (Fe3O4)

mineral