igneous

Granodiorite

Granodiorite (Quartz + Plagioclase + Alkali Feldspar + Biotite/Hornblende)

Hardness: 6-7 Mohs; Color: Mottled black and white ('salt and pepper'); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible crystals); Specific gravity: 2.6-2.7

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

Identified March 30, 2026More igneous →

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Physical properties

Hardness: 6-7 Mohs; Color: Mottled black and white ('salt and pepper'); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible crystals); Specific gravity: 2.6-2.7

Formation & geological history

Formed through the slow cooling of silica-rich magma deep within the Earth's crust (plutonic). It is common in batholiths associated with mountain-building subduction zones, often dating from the Archean to the Cenozoic eras.

Uses & applications

Used widely in heavy construction, road surfacing, and as ornamental stone (granite-style countertops and monuments). It is also a primary host rock for porphyry copper deposits.

Geological facts

Famous structures made of granodiorite include the Rosetta Stone and the base of the Statue of Liberty. It is intermediate in composition between granite and diorite, containing more plagioclase than orthoclase.

Field identification & locations

Identify in the field by its coarse 'salt and pepper' appearance and visible quartz grains. It can be distinguished from granite by its lower potassium feldspar content (less pink/orange) and higher dark mineral content. It is extremely common in the Sierra Nevada mountains and the Andes.

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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