igneous
Granodiorite
Granodiorite (calc-alkaline phaneritic igneous rock)
Hardness: 6-7 (Mohs); Color: Mottled salt-and-pepper (white, grey, and dark green/black); Luster: Dull to vitreous; Crystal Structure: Phaneritic (medium-to-coarse grained); Specific Gravity: 2.65-2.73.
- Hardness
- 6-7 (Mohs)
- Color
- Mottled salt-and-pepper (white, grey, and dark green/black)
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 (Mohs); Color: Mottled salt-and-pepper (white, grey, and dark green/black); Luster: Dull to vitreous; Crystal Structure: Phaneritic (medium-to-coarse grained); Specific Gravity: 2.65-2.73.
Formation & geological history
Formed through the slow cooling of silica-rich magma beneath the Earth's surface (intrusive). Usually found in large batholiths associated with mountain building or subduction zones. Common in the Phanerozoic eon.
Uses & applications
Predominantly used as crushed stone for road construction and concrete aggregate. Also common as ornamental 'granite' for countertops, paving stones, and monument building.
Geological facts
The famous Rosetta Stone was carved into a block of granodiorite rather than basalt as previously thought. It is the most common rock type in the Sierra Nevada batholith of California.
Field identification & locations
Identify by its interlocking 'salt and pepper' crystals. Look for more dark minerals (biotite/hornblende) and plagioclase compared to standard granite. Found globally in mountain ranges and cratons.
