igneous
Granodiorite Pebble
Granodiorite
Hardness: 6-7 (Mohs); Color: Mottled gray with black and white salt-and-pepper appearance; Luster: Dull to vitreous when wet; Structure: Phaneritic (medium-grained crystalline); Specific Gravity: 2.6-2.7
- Hardness
- 6-7 (Mohs)
- Color
- Mottled gray with black and white salt-and-pepper appearance
- Luster
- Dull to vitreous when wet
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Physical properties
Hardness: 6-7 (Mohs); Color: Mottled gray with black and white salt-and-pepper appearance; Luster: Dull to vitreous when wet; Structure: Phaneritic (medium-grained crystalline); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the slow cooling of silica-rich magma beneath the Earth's surface (intrusive). This specific specimen has been rounded by fluvial or glacial transport over thousands of years.
Uses & applications
Used primarily as crushed stone for road base, concrete aggregate, and dimension stone for countertops or monuments. Small pebbles like this are used in landscaping or as decorative river rock.
Geological facts
Granodiorite is the intermediate rock between granite and diorite. Famous historical artifacts, including the Rosetta Stone, were carved from granodiorite.
Field identification & locations
Identify by its phaneritic texture showing quartz, plagioclase, and dark mafic minerals like biotite. Commonly found in mountainous riverbeds or glacial tills. Collectors look for unique inclusions or high polish.
