igneous
Granodiorite
Granodiorite
Hardness: 6-7 (Mohs); Color: Mottled grey, white, and black; Luster: Phaneritic (crystalline); Structure: Massive/Granular; Cleavage: None (fractures); Specific Gravity: 2.6-2.7
- Hardness
- 6-7 (Mohs)
- Color
- Mottled grey, white, and black
- Luster
- Phaneritic (crystalline)
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Physical properties
Hardness: 6-7 (Mohs); Color: Mottled grey, white, and black; Luster: Phaneritic (crystalline); Structure: Massive/Granular; Cleavage: None (fractures); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground (plutonic). It is intermediate in composition between granite and diorite. Found in large mountain ranges and continental crust.
Uses & applications
Commonly used as crushed stone for road construction, railroad ballast, and building foundations. High-quality specimens are polished for use as countertops and architectural stone.
Geological facts
Granodiorite is the rock that makes up the famous Rosetta Stone. It is much more abundant in the Earth's continental crust than true granite, even though people often confuse the two.
Field identification & locations
Identify by its 'salt and pepper' appearance with crystals visible to the naked eye. It contains more plagioclase feldspar than orthoclase. Found in batholiths and mountain ranges like the Sierra Nevada.
