igneous
Granodiorite
Granodiorite (Intermediate intrusive igneous rock)
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (mottled grey, white, and black with occasional pinkish feldspar). Luster: Phaneritic (crystalline). Structure: Coarse-grained intrusive. Specific Gravity: 2.6-2.7.
- Hardness
- 6-7 on Mohs scale
- Luster
- Phaneritic (crystalline)
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (mottled grey, white, and black with occasional pinkish feldspar). Luster: Phaneritic (crystalline). Structure: Coarse-grained intrusive. Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the slow cooling of silica-rich magma beneath the Earth's surface (plutonic). It is typically associated with volcanic arc subduction zones and is a major component of batholiths.
Uses & applications
Extensively used in construction as crushed stone, road base, and architectural building stone. Polished slabs are used for countertops, floor tiles, and grave markers.
Geological facts
Granodiorite is the rock type that makes up the famous Rosetta Stone. It is intermediate in composition between granite and diorite, containing more plagioclase feldspar than orthoclase.
Field identification & locations
Identify in the field by its coarse-grained texture (visible crystals) and light-to-medium grey color. Look for visible quartz, plagioclase feldspar, and dark minerals like biotite or hornblende. It is common in mountain ranges like the Sierra Nevada.
