igneous

Granodiorite

Phaneritic Plutonic Rock - Granodiorite

Hardness: 6-7 Mohs; Color: Mottled salt-and-pepper (white, grey, and black); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Cleavage: Perfect in feldspar grains; Specific gravity: 2.6-2.7.

Hardness: 6-7 Mohs
Color: Mottled salt-and-pepper (white, grey, and black)
Luster: Vitreous to dull

Identified April 7, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the slow cooling of silica-rich magma deep underground. Common in continental crust and batholiths. Typically formed during orogenic (mountain-building) events across various geological eras.

Uses & applications

Used extensively in construction as crushed stone for roads, and as dimensional stone for monuments, curbing, and countertops. Occasionally used for decorative items.

Geological facts

Granodiorite is the intermediate between granite and diorite. The famous Rosetta Stone was carved from a slab of granodiorite.

Field identification & locations

Identify in the field by its salt-and-pepper appearance and coarse grains. It contains more plagioclase feldspar than orthoclase. Found in major mountain ranges like the Sierra Nevada or the Andes.

Other igneous specimens

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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)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral