sedimentary
Jasper-Agate Conglomerate (Potentially Puddingstone)
Jasper-cemented Silicate Aggregate (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: Mottled red, brown, and tan, Luster: Waxy to dull, Crystal Structure: Microcrystalline trigonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.9
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Mottled red, brown, and tan, Luster: Waxy to dull, Crystal Structure: Microcrystalline trigonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.9
Formation & geological history
Formed through the deposition of rounded pebbles in a fine-grained, silica-rich matrix. Most common specimens like this found in North America were formed during the Huronian Period (roughly 2.3 billion years ago) and transported by glacial activity.
Uses & applications
Used primarily for lapidary work (cabs, beads, and polished stones), garden landscaping, and as a popular decorative rock for amateur collectors.
Geological facts
Often referred to as 'puddingstone' because the rounded pebbles look like raisins in a pudding. In Michigan and Ontario, 'Drummond Island Puddingstone' is highly prized by collectors and used as a regional folk symbol.
Field identification & locations
Identify in the field by its distinct 'clasts' (pebbles) of different colors fused into a single hard rock. It will not scratch with a steel knife. Common in the Great Lakes region, UK, and South Africa. Collectors should look for high contrast between the pebbles and the matrix.
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