Granite Glacial Erratic

Physical Properties

Hardness: 6-7 Mohs; Color: Pink, gray, and black mottled patterns; Luster: Dull (weathered) to vitreous (on fresh surfaces); Crystal structure: Phaneritic (coarse-grained); Specific Gravity: 2.63 to 2.75

Formation & Geological History

Formed from the slow cooling of silica-rich magma deep underground (plutonic). This specific specimen appears to be a glacial erratic, transported and rounded by ice sheets during the Pleistocene Epoch, thousands of years ago.

Uses & Applications

Used in construction, decorative landscaping, aggregate for road building, and as dimension stone for countertops and monuments.

Geological Facts

Granite is the most common igneous rock found on Earth's continents. Glacial erratics like this one can often be found hundreds of miles away from their original bedrock source, which helps geologists trace the path of ancient glaciers.

Field Identification & Locations

Identify in the field by its speckled 'salt and pepper' appearance and visible interlocking crystals of quartz, feldspar, and biotite mica. Look for the rounded, potato-like shape caused by glacial transport or water erosion.

Identified on: 4/22/2026

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