igneous
Granodiorite
Granodiorite (containing Quartz, Plagioclase Feldspar, Biotite, and Hornblende)
Hardness: 6-7 on Mohs scale; Color: typically mottled grey and white with dark flecks; Luster: Vitreous to dull; Crystal structure: Phaneritic (medium-to-coarse grained) holocrystalline; Cleavage: none in the rock mass; Specific gravity: 2.65-2.73.
- Hardness
- 6-7 on Mohs scale
- Color
- typically mottled grey and white with dark flecks
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: typically mottled grey and white with dark flecks; Luster: Vitreous to dull; Crystal structure: Phaneritic (medium-to-coarse grained) holocrystalline; Cleavage: none in the rock mass; Specific gravity: 2.65-2.73.
Formation & geological history
Formed through the slow cooling and crystallization of intermediate to felsic magma deep within the Earth's crust. It is common in batholiths and subduction-related volcanic arcs, spanning from the Archean to the Cenozoic eras.
Uses & applications
Used extensively in construction as crushed stone or 'road metal', dimension stone for building facades, countertops, and occasionally as a base for statues or monuments.
Geological facts
Granodiorite is the rock that makes up the famous Rosetta Stone. It is chemically transitional between granite and diorite, containing more plagioclase than orthoclase feldspar.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible crystals. It has more dark minerals than granite but looks lighter than diorite. It is commonly found in large mountainous plutons like the Sierra Nevada Range.
