igneous
Granodiorite
Granodiorite (Intermediate intrusive igneous rock)
Hardness: 6-7 on Mohs scale; Color: Gray to salt-and-pepper appearance; Luster: Phaneritic/Crystalline; Crystal Structure: Coarse-grained mixture of plagioclase, quartz, and hornblende; Cleavage: Good in feldspars, none in quartz; Specific Gravity: 2.6–2.73.
- Hardness
- 6-7 on Mohs scale
- Color
- Gray to salt-and-pepper appearance
- Luster
- Phaneritic/Crystalline
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Gray to salt-and-pepper appearance; Luster: Phaneritic/Crystalline; Crystal Structure: Coarse-grained mixture of plagioclase, quartz, and hornblende; Cleavage: Good in feldspars, none in quartz; Specific Gravity: 2.6–2.73.
Formation & geological history
Formed through the slow cooling of silica-rich magma beneath the Earth's surface (plutonic). Found in large batholiths within continental crust, often associated with mountain building events.
Uses & applications
Used primarily in heavy construction as crushed stone, road base, and architectural building stone. High-quality specimens are used for countertops, monuments, and paving stones.
Geological facts
Granodiorite is the main component of the famous Yosemite National Park cliffs and was the rock type used to carve the Rosetta Stone. It has a higher concentration of plagioclase feldspar than true granite.
Field identification & locations
Identify in the field by its coarse-grained texture and the presence of more white/gray plagioclase than pink potassium feldspar. Commonly found in subduction zones and large continental shield areas. Collectors look for large, well-defined crystals.
