igneous
Granodiorite
Phaneritic Plutonic Rock (Granodiorite)
Hardness: 6-7 Mohs; Color: Mottled gray, black, and white; Luster: Dull to vitreous; Crystal structure: Phaneritic (visible interlocking crystals); Cleavage: Perfect on feldspars; Specific gravity: 2.6-2.7
- Hardness
- 6-7 Mohs
- Color
- Mottled gray, black, and white
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Mottled gray, black, and white; Luster: Dull to vitreous; Crystal structure: Phaneritic (visible interlocking crystals); Cleavage: Perfect on feldspars; Specific gravity: 2.6-2.7
Formation & geological history
Formed from the slow cooling of silica-rich magma deep within the Earth's crust (intrusive). They are often found in batholiths and associated with convergent plate boundaries and mountain-building events.
Uses & applications
Used widely in construction as crushed stone, 'granite' countertops, paving stones, and for monuments or ornamental architecture.
Geological facts
Granodiorite is the most common rock found in the Sierra Nevada batholith. The famous 'Stonehenge' includes some components of similar igneous origin, and the Rosetta Stone was carved from granodiorite.
Field identification & locations
Identify by looking for a 'salt and pepper' appearance with more white/gray plagioclase than pink potassium feldspar. It is common in mountainous regions and can be found in glacial till.
