sedimentary

Glacial Erratic Boulder (Sandstone / Granite)

Glacial Erratic / Sandstone (SiO2 dominated)

AI-generated identification · may be incorrect

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

Identified July 22, 2026More sedimentary →

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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.