Granodiorite

Physical Properties

Hardness: 6-7 on Mohs scale; Color: Salt-and-pepper (white, gray, and black); Luster: Phaneritic (crystalline); Crystal Structure: Granular/Coarse-grained; Cleavage: Varies by mineral constituent; Specific Gravity: 2.6-2.7

Formation & Geological History

Formed through the slow cooling of silica-rich magma beneath the Earth's surface (intrusive). They typically occur in large batholiths associated with mountain building along subduction zones.

Uses & Applications

Major use in construction as crushed stone or 'granite' slabs for countertops, building facades, and paving stones. Is also used for monuments and statues.

Geological Facts

Granodiorite is the rock that makes up the famous Rosetta Stone. It is intermediate in composition between granite and diorite, containing more plagioclase feldspar than orthoclase.

Field Identification & Locations

Identify by its coarse-grained 'salt and pepper' look; look for visible crystals of quartz, plagioclase, and dark biotite or hornblende. It is frequently found in the Sierra Nevada and other major mountain ranges.

Identified on: 4/14/2026

Mode: Standard