igneous
Granodiorite
Phaneritic intrusive igneous rock
Hardness: 6-7 on Mohs scale; Color: Light gray to dark gray with a speckled appearance; Luster: Dull to sub-vitreous; Crystal structure: Coarse-grained (phaneritic) texture with visible plagioclase feldspar, quartz, and biotite or hornblende; Specific gravity: 2.65-2.75
- Hardness
- 6-7 on Mohs scale
- Color
- Light gray to dark gray with a speckled appearance
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Light gray to dark gray with a speckled appearance; Luster: Dull to sub-vitreous; Crystal structure: Coarse-grained (phaneritic) texture with visible plagioclase feldspar, quartz, and biotite or hornblende; Specific gravity: 2.65-2.75
Formation & geological history
Formed from the slow cooling and solidification of magma rich in silica and intermediate between granite and diorite beneath the Earth's crust, typically over millions of years.
Uses & applications
Used primarily as dimension stone, crushed stone for construction, architectural facings, and occasionally as monumental stone.
Geological facts
Granodiorite is very similar in appearance to granite, but contains a higher proportion of plagioclase feldspar relative to alkali feldspar. The famous Rosetta Stone is carved from a slab of granodiorite rather than basalt as was commonly believed for centuries.
Field identification & locations
Can be identified in the field by its speckled, salt-and-pepper appearance consisting mainly of white/gray feldspar, clear-to-gray quartz, and dark biotite mica or hornblende. Commonly found in major batholiths and mountain-building zones worldwide.
