sedimentary

Puddingstone (Gowganda Tillite/Lorrain Quartzite)

Jasper Conglomerate

Hardness: 6.5-7 (Mohs), Color: Brownish-red to tan matrix with colorful rounded pebbles of red jasper, white quartz, and black chert. Luster: Dull matrix, vitreous pebbles. Structure: Clastic sedimentary.

Hardness: 6
Luster: Dull matrix, vitreous pebbles

Identified May 18, 2026More sedimentary →

Explore Puddingstone (Gowganda Tillite/Lorrain Quartzite) in the encyclopedia →

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Physical properties

Formation & geological history

Formed roughly 2.2 to 2.4 billion years ago during the Paleoproterozoic era. It originated as river-deposited gravel and sand (Huronian Supergroup) that was eventually buried, compacted, and cemented into stone.

Uses & applications

Primarily used for ornamental purposes, lapidary work (cabs, bookends), landscaping, and as a popular collector item.

Geological facts

The 'Puddingstone' name comes from early British settlers who thought it looked like boiled suet pudding with raisins and fruit. It is functionally a glacial erratic in many locations, moved south by glaciers during the last Ice Age.

Field identification & locations

Identify by looking for distinct, colorful rounded jasper pebbles embedded in a hard, sandy quartz matrix. Commonly found in the St. Joseph Island area of Ontario and through the Great Lakes region, especially Michigan and Ohio.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Cone-in-cone structure (Limestone)

Cone-in-cone structure (Secondary Sedimentary Structure)

sedimentary

Chert Breccia

Brecciated Chert (Microcrystalline Silica)

sedimentary

Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

sedimentary

Shale or Slaty Mudstone

Argillaceous sedimentary rock

sedimentary

Sandstone

Arenite (primarily SiO2)

sedimentary