igneous

Granodiorite

Granodiorite (calc-alkaline phaneritic igneous rock)

Hardness: 6-7 (Mohs); Color: Mottled salt-and-pepper (white, grey, and dark green/black); Luster: Dull to vitreous; Crystal Structure: Phaneritic (medium-to-coarse grained); Specific Gravity: 2.65-2.73.

Hardness: 6-7 (Mohs)
Color: Mottled salt-and-pepper (white, grey, and dark green/black)
Luster: Dull to vitreous

Identified March 23, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow cooling of silica-rich magma beneath the Earth's surface (intrusive). Usually found in large batholiths associated with mountain building or subduction zones. Common in the Phanerozoic eon.

Uses & applications

Predominantly used as crushed stone for road construction and concrete aggregate. Also common as ornamental 'granite' for countertops, paving stones, and monument building.

Geological facts

The famous Rosetta Stone was carved into a block of granodiorite rather than basalt as previously thought. It is the most common rock type in the Sierra Nevada batholith of California.

Field identification & locations

Identify by its interlocking 'salt and pepper' crystals. Look for more dark minerals (biotite/hornblende) and plagioclase compared to standard granite. Found globally in mountain ranges and cratons.

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

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral