sedimentary (cryptocrystalline quartz)
Jasper River Pebble
Jasper (Silicon Dioxide, SiO2)
Hardness: 6.5–7 (Mohs scale); Color: Brown, tan, reddish; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.91.
- Hardness
- 6
- Color
- Brown, tan, reddish
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Brown, tan, reddish; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.91.
Formation & geological history
Formed from the precipitation of silica from groundwater in volcanic ash or sedimentary deposits, often during the Paleozoic to Cenozoic eras. This specimen has been rounded into a pebble by fluvial (river) erosion.
Uses & applications
Commonly used in lapidary work for cabochons and beads, as aquarium decor, or as landscape gravel. In ancient times, it was used for seals and amulets.
Geological facts
Jasper is an opaque variety of chalcedony. The reddish-brown spots are typically caused by iron inclusions (hematite). It has been used for over 5,000 years in jewelry and sculpture due to its hardness and ability to take a high polish.
Field identification & locations
Identify in the field by its opacity (it does not transmit light even at the edges), smooth texture when wet, and inability to be scratched by a steel knife. Commonly found in riverbeds, gravel bars, and coastal areas.
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