Gowganda Tillite (Puddingstone)

Physical Properties

Hardness: 6.5-7 (Mohs); Color: White to grey matrix with red jasper clasts; Luster: Dull to waxy; Structure: Conglomerate/Breccia; Cleavage: None

Formation & Geological History

Formed during the Huronian glaciation approximately 2.2 to 2.4 billion years ago. It is a lithified glacial deposit where rocks were trapped in ice and later settled into a fine-grained silty matrix.

Uses & Applications

Primarily used as a lapidary material for jewelry, paperweights, and decorative ornaments. Historically used in localized construction but now a popular collector's item.

Geological Facts

This specific variety is often called 'Michigan Puddingstone' or 'St. Joseph Island Puddingstone'. It is one of the oldest known glacial deposits on Earth, marking a 'Snowball Earth' period.

Field Identification & Locations

Identify by looking for distinct bright red jasper 'plums' embedded in a harder, lighter-colored quartz or siltstone matrix. Common in the Great Lakes region, especially Michigan and Ontario.

Identified on: 5/15/2026

Mode: Standard