igneous

Granite Pebble

Granite (Phaneritic intrusive igneous rock comprising Quartz, Feldspar, and Mica)

Hardness: 6-7 Mohs; Color: Salt and pepper appearance with pink/white feldspar and gray quartz; Luster: Dull (weathered) to Vitreous (internal); Structure: Phaneritic (coarse-grained); Cleavage: None for whole rock, but individual feldspar grains show 2 planes.

Hardness: 6-7 Mohs
Luster: Dull (weathered) to Vitreous (internal)

Identified March 2, 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 anthropogenically or naturally rounded by water erosion in a river, beach, or glacial environment. Geological age ranges from Precambrian to Cenozoic.

Uses & applications

Used extensively in construction (slabs, gravel, dimension stone), monument carving, and as high-durability kitchen countertops. Small river pebbles like this are used in landscaping and aquarium decor.

Geological facts

Granite makes up the majority of Earth's continental crust. It is one of the hardest and most resistant common rocks, which is why it remains as rounded pebbles even after softer rocks have eroded away.

Field identification & locations

Identify in the field by its 'salt and pepper' grainy texture where distinct mineral crystals (pink/white/white/black) can be seen with the naked eye. It will not be scratched by a steel knife. Found globally in mountainous regions and glacial till.

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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)

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