Glacial Erratic (Sandstone/Quartzite)

Physical Properties

Hardness: 6-7 (Mohs scale); Color: light grey to tan; Luster: dull to earthy; Crystal structure: granular/clastic; Cleavage: none; Specific Gravity: approx 2.6

Formation & Geological History

Transported by glacial ice during the Last Glacial Period (Pleistocene epoch). These rocks are plucked from their parent bedrock and deposited miles away as the ice melts.

Uses & Applications

Landscaping, historical/geological study, and occasionally as monumental stone or fill material in construction.

Geological Facts

Glacial erratics are 'immigrant' rocks that don't match the local bedrock geology. They provide vital evidence for the direction and extent of ancient ice sheet movements.

Field Identification & Locations

Identify by its rounded shape (abrasion from ice transport) and its placement on top of different soil or rock types. Look for 'glacial striations' or scratches on its surface.

Identified on: 4/25/2026

Mode: Standard