igneous
Granodiorite
Granodiorite (containing Quartz, Plagioclase, Orthoclase, Biotite/Hornblende)
Hardness: 6-7 Mohs; Color: Salt and pepper (white/light gray with black flecks); Luster: Vitreous to pearly; Crystal structure: Phaneritic (coarse-grained); Cleavage: Specific to individual minerals; Specific gravity: 2.6-2.7
- Hardness
- 6-7 Mohs
- Color
- Salt and pepper (white/light gray with black flecks)
- Luster
- Vitreous to pearly
Identified More igneous →
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper (white/light gray with black flecks); Luster: Vitreous to pearly; Crystal structure: Phaneritic (coarse-grained); Cleavage: Specific to individual minerals; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the slow cooling of silica-rich magma deep underground (plutonic). Found in large batholiths forming the cores of mountain ranges, often dating from the Precambrian to the Cenozoic eras.
Uses & applications
Used primarily in heavy construction, road building, and as dimension stone for countertops, floor tiles, and monuments. High-quality specimens are popular for educational use.
Geological facts
Granodiorite is the rock that makes up the famous Rosetta Stone. It is intermediate between granite and diorite in chemical composition.
Field identification & locations
Identify by its coarse-grained texture and 'salt and pepper' appearance. Look for more plagioclase feldspar than orthoclase. Commonly found in batholiths like the Sierra Nevada mountain range.
