igneous
Granodiorite
Granodiorite (containing Plagioclase, Quartz, K-Feldspar, and Hornblende or Biotite)
Hardness: 6-7 (Mohs scale); Color: Salt and pepper with pinkish hues; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained); Cleavage: Distinct in feldspars; Specific gravity: 2.6-2.7
- Hardness
- 6-7 (Mohs scale)
- Color
- Salt and pepper with pinkish hues
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Salt and pepper with pinkish hues; Luster: Dull to vitreous; Crystal structure: Phaneritic (coarse-grained); Cleavage: Distinct in feldspars; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the slow cooling of silica-rich magma deep underground (plutonic) within continental crust, typically in subduction zones or volcanic arcs during the Mesozoic or Cenozoic eras.
Uses & applications
Used primarily in heavy construction, road building, as dimension stone for countertops and tiles, and as landscaping material. Fine specimens are used for teaching geological identification.
Geological facts
The Rosetta Stone was famously carved into a slab of granodiorite, not basalt as previously thought. It is the most common intrusive rock found in the Sierra Nevada Batholith.
Field identification & locations
Identify by its 'salt and pepper' appearance often mixed with salmon-colored orthoclase. Found in mountainous or glaciated regions. Collectors look for large crystal individualization and lack of weathering.
