igneous

Granite

Phaneritic Felsic Igneous Rock (primarily Quartz, Feldspar, and Mica)

Hardness: 6-7 on Mohs scale. Color: Mottled salt-and-pepper appearance with shades of white, pink, and grey/black. Luster: Dull to vitreous. Crystal structure: Coarse-grained phaneritic (visible crystals). Specific gravity: 2.63 to 2.75.

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

Identified March 21, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow crystallization of magma below the Earth's surface (intrusive). Most continental granite dates from the Precambrian to Cenozoic eras, found primarily in batholiths and continental crust.

Uses & applications

Extensively used in construction for countertops, floor tiles, paving stones, and monuments due to its durability. Small river-worn specimens like this are used in landscaping or as decorative stones.

Geological facts

Granite makes up much of the Earth's continental crust. Mount Rushmore is carved into a granite batholith. It is one of the hardest and most durable common stones on Earth.

Field identification & locations

Identify by its interlocking 'salt and pepper' crystalline texture and extreme hardness (it will scratch glass). Commonly found in mountain ranges, glaciated areas, and as rounded pebbles on beaches or in riverbeds.

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