sedimentary
Chert (specifically Yellow Jasper variety)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Ochre yellow to tan. Luster: Waxy to dull. Crystal structure: Cryptocrystalline (microscopic quartz). Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.
- Hardness
- 6
- Color
- Ochre yellow to tan
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Ochre yellow to tan. Luster: Waxy to dull. Crystal structure: Cryptocrystalline (microscopic quartz). Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the accumulation of silica-rich microfossils or precipitation from hydrothermal fluids. This specimen appears to be a fragment showing a conchoidal fracture pattern typical of silica-based sedimentary rocks.
Uses & applications
Historically used for stone tools (knapping). Currently used for lapidary work, jewelry, landscaping, and as a component in construction aggregate.
Geological facts
Yellow jasper was historically associated with protection and spiritual endurance. It is essentially a variety of chert that is opaque due to high iron oxide (limonite) content.
Field identification & locations
Identify in the field by its waxy texture and sharp, curved (conchoidal) edges when broken. It will scratch glass but cannot be scratched by a steel knife. Commonly found in riverbeds and limestone formations.
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