igneous
Granite Glacial Erratic Boulder
Granite
Hardness: 6-7 on Mohs scale; Color: light greyish-green to buff with weathering and moss/lichen surface growth; Luster: dull to earthy on weathered surface, vitreous on fresh breaks; Structure: phaneritic (coarse-grained) crystalline texture; Cleavage: none.
- Hardness
- 6-7 on Mohs scale
Identified More igneous →
Explore Granite Glacial Erratic Boulder in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 on Mohs scale; Color: light greyish-green to buff with weathering and moss/lichen surface growth; Luster: dull to earthy on weathered surface, vitreous on fresh breaks; Structure: phaneritic (coarse-grained) crystalline texture; Cleavage: none.
Formation & geological history
Formed deep underground from the slow cooling and crystallization of silica-rich magma. Later eroded, transported, and rounded by glacial ice sheets during the last glacial period, creating smooth glacial erratic boulders.
Uses & applications
Used in landscaping, decorative outdoor boulders, erosion control, retainage walls, and historical stone masonry.
Geological facts
Glacial erratics are rocks that differ from the size and type of rock native to the area in which they rest. They were carried by glacial ice, often over hundreds of miles, before being deposited when the ice melted.
Field identification & locations
Identify by its large, rounded form resting on soil surface in glaciated regions, featuring visible coarse quartz and feldspar grains under surface weathering. Extremely common throughout northern North America and Europe.
