Granodiorite

Physical Properties

Hardness: 6-7 (Mohs); Color: Mottled grey, white, and black; Luster: Dull to sub-vitreous; Structure: Phaneritic (coarse-grained); Cleavage: Poor; Specific Gravity: 2.6-2.7

Formation & Geological History

Formed from the slow cooling of silica-rich magma below the Earth's surface in batholiths and continental crustal margins, typically during mountain-building events (Orogeny).

Uses & Applications

Used widely in heavy construction, road building as crushed stone, and as decorative dimension stone for countertops, flooring, and monuments.

Geological Facts

Granodiorite is the rock that makes up the famous Rosetta Stone. It is the intermediate rock between granite and diorite and is a major component of the Earth's continental crust.

Field Identification & Locations

Identify in the field by its 'salt and pepper' appearance and visible crystals of plagioclase feldspar, quartz, and dark biotite or hornblende. Commonly found in subduction zone mountain ranges like the Sierra Nevada.

Identified on: 5/1/2026

Mode: Standard