sedimentary

Puddingstone (Jasper Conglomerate)

Jasper Conglomerate (SiO2 matrix with Fe2O3 inclusions)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs); Color: White to tan matrix with red and brown inclusions; Luster: Dull to waxy; Structure: Clastic; Cleavage: None; SG: 2.6-2.7

Hardness: 6
Color: White to tan matrix with red and brown inclusions
Luster: Dull to waxy

Identified March 29, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: White to tan matrix with red and brown inclusions; Luster: Dull to waxy; Structure: Clastic; Cleavage: None; SG: 2.6-2.7

Formation & geological history

Formed during the Huronian Supergroup (Paleoproterozoic era, ~2.3 billion years ago) through the cementing of rounded jasper pebbles within a quartz sand matrix under high pressure.

Uses & applications

Used primarily for ornamental stone carving, lapidary jewelry (cabs), landscaping, and as a popular collector's specimen due to its unique appearance.

Geological facts

St. Joseph Island in Ontario is famous for these; the 'pudding' name comes from British settlers who thought it looked like boiled suet pudding with raisins and currants.

Field identification & locations

Identify by looking for distinct, smooth red jasper 'plums' embedded in a gritty white quartz or quartzite matrix. Primarily found in the Great Lakes region, especially Michigan and Ontario.