sedimentary
Puddingstone (Gowganda)
Jasper-clast Polymictic Conglomerate (Gowganda Formation)
Hardness: 6.5-7 (quartz-rich clasts); Color: Dark grey to reddish-brown matrix with red, black, and white clasts; Luster: Dull/earthy matrix with vitreous clasts; Structure: Clastic; Cleavage: None.
- Hardness
- 6
- Luster
- Dull/earthy matrix with vitreous clasts
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Physical properties
Hardness: 6.5-7 (quartz-rich clasts); Color: Dark grey to reddish-brown matrix with red, black, and white clasts; Luster: Dull/earthy matrix with vitreous clasts; Structure: Clastic; Cleavage: None.
Formation & geological history
Formed during the Huronian Glaciation (approx. 2.2 to 2.4 billion years ago) through glacial deposition and subsequent lithification of outwash gravels.
Uses & applications
Primarily used as a decorative stone, lapidary material for jewelry (cabochons), and as a popular collector's item due to its unique appearance.
Geological facts
The red dots are typically red jasper. The Michigan and Ontario varieties are considered 'glacial erratics' when found far from their original northern source locations.
Field identification & locations
Identify by looking for distinct, colorful rounded pebbles (clasts) embedded in a fine-grained, cemented matrix. Commonly found in the Great Lakes region, especially St. Joseph Island.
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