sedimentary
Jasper
Silicon dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 Mohs; Color: Opaque red and grey; Luster: Vitreous to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Opaque red and grey
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 Mohs; Color: Opaque red and grey; Luster: Vitreous to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
Formation & geological history
Formed from silica-rich fluids precipitating in volcanic ash or sedimentary rocks, often enriched by hydrothermal activity. Red coloration comes from hematite (iron) inclusions.
Uses & applications
Used primarily for lapidary work, jewelry (cabochons), ornamentation, and collection. Historically used for making tools and seals due to hardness.
Geological facts
Jasper is a variety of chalcedony. The name comes from the Greek word 'iaspis', meaning spotted stone. It was mentioned in ancient history as a stone of protection.
Field identification & locations
Identify by its opacity (unlike translucent agate), waxy feel when polished, and inability to be scratched by a steel knife. Frequently found in riverbeds and desert environments.
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