igneous
Granodiorite
Granodiorite (intermediate plutonic rock)
Hardness: 6-7 (Mohs scale); Color: Salt and pepper (mottled grey, white, and black); Luster: Phaneritic (crystalline) minerals are dull to vitreous; Crystal structure: Coarse-grained intrusive; Cleavage: Depends on individual minerals (feldspar/mica); Specific Gravity: 2.6-2.7
- Hardness
- 6-7 (Mohs scale)
- Color
- Salt and pepper (mottled grey, white, and black)
- Luster
- Phaneritic (crystalline) minerals are dull to vitreous
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Salt and pepper (mottled grey, white, and black); Luster: Phaneritic (crystalline) minerals are dull to vitreous; Crystal structure: Coarse-grained intrusive; Cleavage: Depends on individual minerals (feldspar/mica); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the slow cooling of silica-rich magma beneath the Earth's surface (intrusive igneous). It is a major component of batholiths and continental crust, occurring across many geological eras from the Precambrian to the Cenozoic.
Uses & applications
Used in construction as crushed stone for road base, building stone (granite-like facade), monuments, and as high-durability kitchen countertops.
Geological facts
The Rosetta Stone was famously carved into a slab of granodiorite, not basalt as previously thought. It contains more plagioclase feldspar than orthoclase, distinguishing it from true granite.
Field identification & locations
Identify by its coarse 'salt and pepper' look where plagioclase, quartz, biotite, and hornblende are visible. Found in large mountain ranges like the Sierra Nevada. Collectors look for even grain distribution.
