igneous
Granodiorite (Gneissic texture)
Granodiorite (containing Quartz SiO2, Plagioclase Feldspar, and Biotite)
Hardness: 6-7 (Mohs scale); Color: Salt and pepper (gray, white, black); Luster: Dull to vitreous; Crystal structure: Phaneritic/Medium-grained; Cleavage: Poor; Specific gravity: 2.6-2.7
- Hardness
- 6-7 (Mohs scale)
- Color
- Salt and pepper (gray, white, black)
- Luster
- Dull to vitreous
Identified More igneous →
Explore Granodiorite (Gneissic texture) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 (Mohs scale); Color: Salt and pepper (gray, white, black); Luster: Dull to vitreous; Crystal structure: Phaneritic/Medium-grained; Cleavage: Poor; Specific gravity: 2.6-2.7
Formation & geological history
Formed from the slow cooling of silica-rich magma below the Earth's surface. This specimen appears to have mild metamorphic alignment (gneissic character), suggesting it was subjected to heat and pressure after its initial igneous formation.
Uses & applications
Used primarily in heavy construction, road base, and as decorative dimension stone (frequently sold as 'granite' in the countertop industry).
Geological facts
Granodiorite is the rock that makes up the famous Rosetta Stone. It is the intermediate rock between granite and diorite, containing more plagioclase than orthoclase feldspar.
Field identification & locations
Identify by its 'salt and pepper' appearance and hardness (it will scratch glass). Look for the presence of translucent quartz crystals nestled between opaque white feldspars and black mica flakes. Commonly found in large batholiths like the Sierra Nevada mountains.
