igneous

Granite Pebble

Granite (composed primarily of Quartz SiO2, Feldspar KAlSi3O8, and Mica)

Hardness: 6-7 on Mohs scale; Color: Pink, white, and grey mottled appearance; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained visible crystals); Cleavage: Indistinct; Specific gravity: 2.63-2.75

Hardness: 6-7 on Mohs scale
Color: Pink, white, and grey mottled appearance
Luster: Vitreous to dull

Identified April 5, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow crystallization of magma below the Earth's surface (intrusive). These rocks can be hundreds of millions to billions of years old, eventually reaching the surface through erosion and tectonic uplift before being rounded by water action.

Uses & applications

Used extensively in construction (countertops, flooring, monuments) and as decorative landscaping stone. Polished pebbles are popular for aquarium decor and rock tumbling.

Geological facts

Granite makes up a large portion of the Earth's continental crust. El Capitan in Yosemite National Park is one of the most famous granite monoliths in the world.

Field identification & locations

Identify in the field by its 'salt and pepper' or multi-colored speckled appearance with visible interlocking crystals. Common on beaches and in riverbeds where water has smoothed the edges. For collectors, look for unique colors like deep reds or large feldspar inclusions.

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