igneous
Granodiorite
Granodiorite (containing Plagioclase, Quartz, and Biotite)
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (light gray base with dark flecks). Luster: Phaneritic (crystalline/dull). Structure: Coarse-grained intrusive. Specific Gravity: 2.6-2.7.
- Hardness
- 6-7 on Mohs scale
- Color
- Salt-and-pepper (light gray base with dark flecks)
- Luster
- Phaneritic (crystalline/dull)
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (light gray base with dark flecks). Luster: Phaneritic (crystalline/dull). Structure: Coarse-grained intrusive. Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the slow cooling of silica-rich magma deep underground (plutonic). Found in batholiths and continental crust, typically dating from the Archean to the Cenozoic era.
Uses & applications
Used primarily in heavy construction, road building (crushed stone), and as ornamental stone for countertops or monuments (often sold commercially as "granite").
Geological facts
Granodiorite is the rock that makes up the famous Rosetta Stone. It is the most common rock type in the Sierra Nevada mountains of the United States.
Field identification & locations
Identify by its 'salt and pepper' appearance with more white/gray plagioclase than pink potassium feldspar. Commonly found in mountainous regions. Collectors look for large, distinct biotite or hornblende inclusions.
