igneous

Granite Cobble

Granite (Felsic Plutonic Rock)

Hardness: 6-7 on Mohs scale; Color: Salt and pepper (white, gray, black, pink); Luster: Phaneritic (crystalline); Texture: Granular; Specific Gravity: 2.63 - 2.75; Composition: Quartz, Feldspar, and Biotite/Mica.

Hardness: 6-7 on Mohs scale
Color: Salt and pepper (white, gray, black, pink)
Luster: Phaneritic (crystalline)

Identified April 11, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow crystallization of magma below Earth's surface. This specific specimen has been chemically and physically weathered into a rounded cobble, likely transported by water or glacial activity. Granite can date from the Precambrian to the Cenozoic eras.

Uses & applications

Used widely in construction (countertops, flooring, monuments), as crushed stone for road aggregate, and as landscaping stones. Small river-worn cobbles are popular in decorative garden arrangements.

Geological facts

Granite makes up a large part of the continental crust. It is one of the hardest and most durable common stones, which is why it has been used for everything from Egyptian pyramids to modern skyscrapers.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals of diverse colors. It will not be scratched by a steel nail. Commonly found in mountainous regions or as glacial till 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