igneous
Granodiorite
Granodiorite
Hardness: 6-7 on Mohs scale. Color: Mottled gray, white, and pinkish-tan with dark specks. Luster: Dull to sub-vitreous. Crystal structure: Phaneritic (medium to coarse-grained), equigranular. Specific gravity: 2.6-2.7.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled gray, white, and pinkish-tan with dark specks
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Mottled gray, white, and pinkish-tan with dark specks. Luster: Dull to sub-vitreous. Crystal structure: Phaneritic (medium to coarse-grained), equigranular. Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the slow cooling of silica-rich magma beneath the Earth's surface (plutonic). It is intermediate in composition between granite and diorite. Found in large batholiths often associated with mountain-building events (orogenies).
Uses & applications
Used primarily in heavy construction, road base, and as crushed stone. Polished slabs are used for countertops, floor tiles, and building veneers, similar to granite.
Geological facts
Granodiorite is the most common intrusive rock in the Earth's crust. The famous Rosetta Stone was carved from a slab of granodiorite, not basalt as was originally thought.
Field identification & locations
Identify by its 'salt and pepper' appearance with a higher ratio of plagioclase feldspar than orthoclase. Commonly found in the Sierra Nevada mountains and other volcanic arc roots. Look for visible crystals of quartz, feldspar, and dark minerals like biotite or hornblende.
