sedimentary
Red Jasper Conglomerate (Puddingstone)
Silicified Conglomerate (SiO2 with inclusions)
Hardness: 6.5-7 on Mohs scale. Color: Brownish-gray matrix with distinct red jasper clasts. Luster: Dull to waxy. Structure: Clastic/Granular. Cleavage: None (conchoidal fracture on clasts).
- Hardness
- 6
- Color
- Brownish-gray matrix with distinct red jasper clasts
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Brownish-gray matrix with distinct red jasper clasts. Luster: Dull to waxy. Structure: Clastic/Granular. Cleavage: None (conchoidal fracture on clasts).
Formation & geological history
Formed during the Paleoproterozoic era (approx. 2.3 billion years ago). It consists of rounded pebbles of jasper and quartz cemented together by a fine-grained quartzite matrix, typically in a high-energy river or glacial environment.
Uses & applications
Used for lapidary work, decorative cabochons, garden landscaping, and as a popular collector specimen for those interested in glacial erratics and ancient earth history.
Geological facts
The most famous variety is the St. Joseph Island Puddingstone from Ontario, Canada. These rocks were transported by glaciers during the last Ice Age across the Great Lakes region.
Field identification & locations
Identified by the contrast between a hard, light-colored matrix and embedded rounded red jasper stones. Commonly found on beaches and in glacial till throughout the Michigan and Ontario regions.
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