sedimentary

Puddingstone

Polymictic Conglomerate

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: Cream or gray matrix with red, brown, or black clasts, Luster: Dull to waxy, Crystal structure: Amorphous/Microcrystalline, Specific gravity: 2.6-2.7

Hardness: 6

Identified June 17, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Cream or gray matrix with red, brown, or black clasts, Luster: Dull to waxy, Crystal structure: Amorphous/Microcrystalline, Specific gravity: 2.6-2.7

Formation & geological history

Formed through the deposition of rounded jasper pebbles and quartz sand in high-energy river environments, subsequently lithified by silica cement roughly 2.3 billion years ago (Huronian Supergroup).

Uses & applications

Used primarily for lapidary work, jewelry, ornamental carvings, and as a popular collector's item due to its unique aesthetic appearance.

Geological facts

Famous varieties include the St. Joseph Island Puddingstone found in the Great Lakes region and the Hertfordshire Puddingstone in the UK, which was once believed to ward off evil.

Field identification & locations

Identify by looking for rounded red jasper 'raisins' embedded in a very hard, light-colored quartzite matrix. Commonly found on beaches along the North Shore of Lake Huron and throughout Michigan.