igneous
Granodiorite
Intermediate Phaneritic Plutonic Rock
Hardness: 6-7 on Mohs scale; Color: Salt and pepper (white/grey with black/green flecks); Luster: Vitreous to dull; Crystal structure: Phaneritic (visible crystals of quartz, plagioclase, and biotite/hornblende); Specific Gravity: 2.6-2.7.
- Hardness
- 6-7 on Mohs scale
- Color
- Salt and pepper (white/grey with black/green flecks)
- Luster
- Vitreous to dull
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 on Mohs scale; Color: Salt and pepper (white/grey with black/green flecks); Luster: Vitreous to dull; Crystal structure: Phaneritic (visible crystals of quartz, plagioclase, and biotite/hornblende); Specific Gravity: 2.6-2.7.
Formation & geological history
Formed by the slow cooling of silica-rich magma deep underground (plutonic). This specimen shows weathering and water-rounding, likely found in a river or glacial deposit. Can range from Precambrian to Cenozoic in age.
Uses & applications
Used extensively as crushed stone for road construction, as dimension stone for building facades and countertops, and occasionally for commemorative monuments.
Geological facts
Granodiorite is the intermediate rock between granite and diorite. The famous Rosetta Stone was carved from a slab of granodiorite, not basalt as originally thought.
Field identification & locations
Identify in the field by looking for a coarse-grained texture where light-colored plagioclase feldspar exceeds potassium feldspar, mixed with dark mafic minerals. Found globally in continental crust and batholiths.
