igneous

Granite Pebble (River Rock)

Phaneritic Felsic Igneous Rock

Hardness: 6-7 Mohs; Color: Mottled cream, tan, and grey; Luster: Dull to vitreous; Crystal structure: Phaneritic (visible interlocking crystals); Cleavage: Indistinct; Specific gravity: Approx 2.6-2.7.

Hardness: 6-7 Mohs
Color: Mottled cream, tan, and grey
Luster: Dull to vitreous

Identified April 12, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow cooling of silica-rich magma deep underground. This specific specimen has been shaped and smoothed by fluvial (river) erosion or shoreline Wave action over a period of many years to centuries.

Uses & applications

Used primarily for landscaping, decorative garden stones, and as aquarium substrate. In bulk, granite is used in construction and for kitchen countertops.

Geological facts

Granite makes up a large portion of the Earth's continental crust. Because of its hardness, it survives long journeys down rivers, eventually becoming these smooth, oval-shaped 'worry stones'.

Field identification & locations

Identify by its speckled 'salt and pepper' appearance and its extreme hardness; it will scratch glass and cannot be scratched by a steel knife. Commonly found in riverbeds, glacial deposits, and beaches.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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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)

mineral