sedimentary
Glacial Erratic Boulder (Sandstone / Granite)
Glacial Erratic / Sandstone (SiO2 dominated)
Hardness: 6-7 on Mohs scale depending on composition. Color: Light grayish-brown to tan. Luster: Dull to earthy. Texture: Medium-grained, rounded and smoothed surface due to weathering and transport.
- Hardness
- 6-7 on Mohs scale depending on composition
- Color
- Light grayish-brown to tan
- Luster
- Dull to earthy
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Physical properties
Hardness: 6-7 on Mohs scale depending on composition. Color: Light grayish-brown to tan. Luster: Dull to earthy. Texture: Medium-grained, rounded and smoothed surface due to weathering and transport.
Formation & geological history
Formed by sedimentary deposition or igneous crystallization, then detached, transported, and rounded by glacial ice movement during the Pleistocene epoch thousands of years ago.
Uses & applications
Used in landscape architecture, decorative stone placement, retaining walls, and outdoor play structures.
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 over long distances, sometimes hundreds of miles.
Field identification & locations
Look for large, rounded, isolated boulders sitting on top of till or soil that differ compositionally from local bedrock. Frequently found in glaciated regions of North America and Europe.
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