Granodiorite

Physical Properties

Hardness: 6-7 Mohs; Color: Salt and pepper (mottled grey, white, and pinkish-brown); Luster: Phaneritic (visible crystals), vitreous to dull; Crystal Structure: Massive, granular; Cleavage: Good in feldspar minerals.

Formation & Geological History

Formed through the slow cooling of silica-rich magma beneath the Earth's surface (intrusive/plutonic). They are commonly found in the roots of mountain belts (batholiths) and oceanic-continental subduction zones.

Uses & Applications

Used primarily as crushed stone for road construction and as an ornamental architectural stone. High-quality slabs are sometimes sold as 'granite' for countertops.

Geological Facts

Granodiorite is the intermediate step between granite and diorite. The famous Rosetta Stone was carved into a slab of granodiorite.

Field Identification & Locations

Identify in the field by its speckled appearance and 'salt and pepper' texture. It contains more plagioclase feldspar than orthoclase, often giving it a slightly darker look than true granite. Found ubiquitously in mountain ranges like the Sierra Nevada.

Identified on: 4/14/2026

Mode: Standard