igneous

Granite Pebble

Granite (Phaneritic intrusive igneous rock)

Hardness: 6-7 Mohs; Color: Speckled pink, white, and grey; Luster: Vitreous to dull; Crystal structure: Coarse-grained (phaneritic); Cleavage: Variable based on mineral content (perfect on feldspar faces); TG: 2.63 to 2.75

Hardness: 6-7 Mohs
Color: Speckled pink, white, and grey
Luster: Vitreous to dull

Identified June 2, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow crystalline cooling of magma beneath the Earth's surface (plutonic). Found globally in continental crust, often dating from the Precambrian to Cenozoic eras.

Uses & applications

Used extensively in construction (curbstones, floor tiles, countertops), as crushed stone for road bases, and as architectural stone.

Geological facts

Granite makes up a large portion of the Earth's continental crust. It is often the core of mountain ranges. Famous peaks like El Capitan and Mount Rushmore are carved from granite.

Field identification & locations

Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals of quartz, feldspar, and mica. This specific specimen appears to be a water-worn or weathered fragment common in riverbeds and gravel driveways.

Other igneous specimens

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Granite

Igneous

Granite

Igneous

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dalmatian Jasper

Aplite with Arfvedsonite inclusions

igneous

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