igneous

Granodiorite (River Rock / Cobble)

Granodiorite; Phaneritic intrusive igneous rock dominated by plagioclase, quartz, and hornblende/biotite

Hardness: 6-7 on Mohs scale. Color: Mottled salt-and-pepper appearance with grey, black, and pinkish-white tones. Luster: Dull (weathered) to vitreous (broken surface). Texture: Phaneritic (medium to coarse-grained crystals).

Hardness: 6-7 on Mohs scale
Luster: Dull (weathered) to vitreous (broken surface)

Identified April 11, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling of silica-rich magma beneath the Earth's surface (plutonic). This specific specimen has been smoothed and rounded by long-term transport in water (fluvial or glacial processes).

Uses & applications

Used primarily in construction as crushed stone, road base, and decorative landscaping. High-quality slabs are sometimes used for countertops ('granite').

Geological facts

Granodiorite is geographically widespread and makes up a significant portion of the Earth's continental crust. It is the rock type that makes up the famous Rosetta Stone.

Field identification & locations

Identify in the field by its visible interlocking crystals and the presence of more white/grey plagioclase than pink potassium feldspar. Commonly found in riverbeds, glacial tills, and mountain ranges.

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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