sedimentary
Jasper Conglomerate
Jasper-clast Conglomerate (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Reddish-brown, cream, tan, and translucent grey. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (microscopic quartz). Specific Gravity: 2.5-2.9.
- Hardness
- 6
- Color
- Reddish-brown, cream, tan, and translucent grey
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Reddish-brown, cream, tan, and translucent grey. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (microscopic quartz). Specific Gravity: 2.5-2.9.
Formation & geological history
Formed through the accumulation of jasper fragments and river gravels that were later cemented together by silica-rich fluids under pressure. Often originates from Precambrian or Paleozoic eras in high-energy fluvial environments.
Uses & applications
Used primarily as decorative stones, in lapidary work for cabochons or tumbled stones, and as garden/landscape accents.
Geological facts
The reddish hues are caused by iron oxide impurities. This specific type is often colloquially called a 'Puddingstone' in regions like Michigan (St. Joseph Island puddingstone), where clasts are suspended in a lighter matrix.
Field identification & locations
Identify by finding a mix of smooth, rounded hard pebbles of different colors cemented into a solid mass that cannot be easily broken apart by hand. Commonly found in Great Lakes glacial drift or ancient riverbeds.
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