Granodiorite

Physical Properties

Hardness: 6-7 (Mohs scale); Color: Salt and pepper (mottled gray, white, and black); Luster: Dull to vitreous; Crystal Structure: Phaneritic (coarse-grained coarse crystals); Cleavage: Individual minerals (feldspar) show perfect cleavage; Specific Gravity: 2.67-2.73

Formation & Geological History

Formed through the slow cooling of silica-rich magma beneath the Earth's surface (intrusive). Usually associated with convergent plate boundaries and subduction zones in continental magmatic arcs.

Uses & Applications

Used extensively in construction as crushed stone for road base, building material, paving stones, and polished for countertops or cemetery monuments.

Geological Facts

Granodiorite is the major component of the Sierra Nevada batholith. The famous 'Rosetta Stone' was carved from a slab of granodiorite, though it was historically misidentified as basalt.

Field Identification & Locations

Identify in the field by its coarse crystalline texture and 'salt and pepper' appearance. Unlike granite, it contains significantly more plagioclase feldspar than orthoclase. Common in mountainous regions like the Andes or Sierra Nevada.

Identified on: 4/22/2026

Mode: Standard