igneous

Granodiorite

Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (mottled gray, white, and black/pinkish-brown). Luster: Phaneritic (crystalline). Structure: Coarse-grained intrusive. Cleavage: Poor. Specific Gravity: 2.6-2.7.

Hardness: 6-7 on Mohs scale
Luster: Phaneritic (crystalline)

Identified January 13, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow cooling of silica-rich magma deep within the Earth's crust (plutonic). Found in batholiths and mountain ranges, often dating from the Mesozoic to Cenozoic eras.

Uses & applications

Used widely in heavy construction as crushed stone, road base, and dimension stone for buildings and monuments. It is also used for countertops and paving.

Geological facts

Granodiorite is the intermediate rock between granite and diorite. One of the most famous historical objects made from granodiorite is the Rosetta Stone, which was once incorrectly identified as basalt.

Field identification & locations

Identify in the field by its coarse crystalline texture and 'salt and pepper' look. It contains more plagioclase feldspar than orthoclase. Commonly found in the Sierra Nevada mountains of California and the Scottish Highlands.

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