sedimentary

Gowganda Tillite (Puddingstone)

Glacial Diamictite (Gowganda Formation)

Hardness: 6-7 (Mohs scale); Color: Brownish-grey to reddish matrix with red jasper and white quartz inclusions; Luster: Dull/Earthy matrix with vitreous clasts; Structure: Massive clastic; Cleavage: None.

Hardness: 6-7 (Mohs scale)
Luster: Dull/Earthy matrix with vitreous clasts

Identified May 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed roughly 2.2 to 2.4 billion years ago during the Huronian glaciation (Paleoproterozoic). It is a lithified glacial till containing fragments of older rocks (clasts) dropped by retreating glaciers.

Uses & applications

Primarily used as a decorative stone in landscaping, for stone masonry, and as a popular lapidary material for jewelry and bookends due to its unique patterns.

Geological facts

This specific variety is often called 'St. Joseph Island Puddingstone'. It is famous for containing bright red jasper clasts within a quartzite matrix, representing some of the oldest glacial deposits on Earth.

Field identification & locations

Identify by looking for distinct rounded red jasper pebbles embedded in a hard, fine-grained matrix. Commonly found as glacial erratics throughout the Great Lakes region, especially in Michigan and Ontario.

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Cone-in-cone structure (Secondary Sedimentary Structure)

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Brecciated Chert (Microcrystalline Silica)

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Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

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Shale or Slaty Mudstone

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Sandstone

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