sedimentary
Puddingstone (Gowganda)
Gowganda Formation Conglomerate
AI-generated identification · may be incorrectHardness 6.5-7 (Mohs scale), tan to brown matrix with red jasper and white quartz inclusions, dull to earthy luster when unpolished, clastic sedimentary structure.
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Physical properties
Hardness 6.5-7 (Mohs scale), tan to brown matrix with red jasper and white quartz inclusions, dull to earthy luster when unpolished, clastic sedimentary structure.
Formation & geological history
Formed roughly 2.3 billion years ago during the Huronian glaciation; it is a glacial tillite where pebbles of jasper and quartz were dropped into a fine-grained silt or sand matrix.
Uses & applications
Used primarily for decorative landscaping, lapidary work (polishing for display), and historic construction in specific regions like St. Joseph Island.
Geological facts
The red pebbles are typically Jasper, and the rock is a famous glacial erratic found across the Great Lakes region, often referred to as St. Joseph Island Puddingstone.
Field identification & locations
Identify by looking for distinct red jasper pebbles embedded in a lighter quartzite or sandstone matrix; commonly found on beaches in Northern Ontario and Michigan.
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