igneous
Granodiorite
Phaneritic intrusive igneous rock
Hardness: 6-7 on Mohs scale; Color: Salt-and-pepper appearance with light gray to white feldspar and dark gray to black biotite/hornblende; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible interlocking crystals); Specific gravity: 2.65-2.75
- Hardness
- 6-7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Salt-and-pepper appearance with light gray to white feldspar and dark gray to black biotite/hornblende; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained, visible interlocking crystals); Specific gravity: 2.65-2.75
Formation & geological history
Formed by the slow cooling and crystallization of magma beneath the Earth's surface, typically in continental convergent plate boundaries.
Uses & applications
Used in construction, as dimension stone for buildings, monument base material, and crushed stone for road aggregates.
Geological facts
Granodiorite is compositionally intermediate between granite and diorite. The famous Rosetta Stone is carved from granodiorite rather than basalt, as was long commonly believed.
Field identification & locations
Can be identified in the field by its intermediate composition showing roughly equal proportions of plagioclase and alkali feldspar, along with quartz and dark minerals like biotite.
