Granodiorite

Physical Properties

Hardness: 6-7 (Mohs scale); Color: Salt and pepper (white to light gray with black specks); Luster: Phaneritic (crystalline); Structure: Coarse-grained granular; Cleavage: None (fractures); Specific Gravity: 2.6-2.7

Formation & Geological History

Formed through the slow cooling of magma rich in silica beneath the Earth's surface (plutonic). It is intermediate between granite and diorite and is a major component of batholiths and continental crust.

Uses & Applications

Used extensively in construction as crushed stone, road base, and dimension stone for countertops, flooring, and building facades.

Geological Facts

Granodiorite is the rock type that makes up the famous Rosetta Stone, which was used to decipher Egyptian hieroglyphs. It also forms much of the Sierra Nevada mountain range in California.

Field Identification & Locations

Identify in the field by its light color compared to diorite and its higher concentration of dark mafic minerals (biotite/hornblende) compared to true granite. Commonly found in subduction zones and large continental mountain belts.

Identified on: 4/24/2026

Mode: Standard