igneous
Granodiorite Pebble
Granodiorite (Intermediate intrusive igneous rock)
Hardness: 6-7 on Mohs scale; Color: Salt-and-pepper (speckled grey, white, and black); Luster: Dull to phaneritic (visible crystals); Crystal Structure: Granular/Holocrystalline; Cleavage: Poor; Specific Gravity: 2.6-2.7
- Hardness
- 6-7 on Mohs scale
- Color
- Salt-and-pepper (speckled grey, white, and black)
- Luster
- Dull to phaneritic (visible crystals)
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Salt-and-pepper (speckled grey, white, and black); Luster: Dull to phaneritic (visible crystals); Crystal Structure: Granular/Holocrystalline; Cleavage: Poor; Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the slow cooling of silica-rich magma beneath the Earth's surface (plutonic). This specific specimen has been rounded through fluvial or glacial erosion, typically occurring over millions of years.
Uses & applications
Used primarily in construction as crushed stone or road base. Larger deposits are used for architectural stone and countertops. This specific smooth specimen is popular for decorative landscaping or as a 'worry stone'.
Geological facts
Granodiorite is the most common rock of the Earth's continental crust. The famous Rosetta Stone was carved from a slab of granodiorite.
Field identification & locations
Identify by its 'salt and pepper' appearance and visible interlocking crystals. It contains more plagioclase feldspar than orthoclase. Commonly found in riverbeds, glacial tills, and mountainous batholiths worldwide.
