sedimentary
Jasper (Green Jasper / Chert)
Silicon Dioxide (SiO2) with iron/clay inclusions
Hardness: 6.5-7 on Mohs scale; Color: Dark olive green; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9.
- Hardness
- 6
- Color
- Dark olive green
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Dark olive green; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9.
Formation & geological history
Formed through the accumulation of silica-rich fluids in volcanic or sedimentary environments. Most jasper dates back to the Precambrian or Paleozoic eras.
Uses & applications
Used primarily for ornamental purposes, jewelry (cabochons), lapidary art, and rock tumbling. Historically used for making tools due to its sharp fracture edges.
Geological facts
Green jasper was a favorite in the ancient world, often called 'rain bringer' and used in amulets. It is an opaque variety of chalcedony.
Field identification & locations
Identify in the field by its smooth, waxy surface when wet and its sharp, shell-like (conchoidal) breakage patterns. It cannot be scratched by a steel knife. Commonly found in riverbeds and coastal areas.
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