sedimentary
Puddingstone (Gowganda Conglomerate)
Polymictic Conglomerate (SiO2 matrix with jasper and quartz inclusions)
Hardness: 6.5-7 Mohs. Color: Creamy white, beige, or pale gray matrix peppered with vivid red jasper pebbles and dark quartz or chert clasts. Luster: Dull to earthy on weathered surfaces, vitreous on fresh fractures. Crystal Structure: Non-crystalline matrix with microcrystalline pebbles. Specific Gravity: ~2.6-2.7.
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 Mohs. Color: Creamy white, beige, or pale gray matrix peppered with vivid red jasper pebbles and dark quartz or chert clasts. Luster: Dull to earthy on weathered surfaces, vitreous on fresh fractures. Crystal Structure: Non-crystalline matrix with microcrystalline pebbles. Specific Gravity: ~2.6-2.7.
Formation & geological history
Formed during the Paleoproterozoic era (approximately 2.2 to 2.4 billion years ago). Originates from glacial tile and stream deposits where rounded red jasper pebbles and quartz were cemented together in a fine-grained sand/silt matrix.
Uses & applications
Used primarily for decorative landscaping, lapidary projects, cabochons, polished display specimens, and as a popular regional collector rock.
Geological facts
Famous varieties like the 'Michigan Puddingstone' or 'St. Joseph Island Puddingstone' were transported southward from Canada across the Great Lakes region by ice age glaciers as glacial erratics.
Field identification & locations
Easily identified by its distinctive 'raisin pudding' appearance: bright red jasper pebbles distinctly standing out against a light-colored, hard matrix. Commonly found along shorelines and glacial drift in Northern Michigan, Ontario, and around Lake Huron.
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