sedimentary
Red Chert (Jasper)
Chert / Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Red/rust due to iron oxide; Luster: Waxy to dull; Crystal structure: Hexagonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 6
- Color
- Red/rust due to iron oxide
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Red/rust due to iron oxide; Luster: Waxy to dull; Crystal structure: Hexagonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolaria) or chemical precipitation in marine environments. The reddish tint specifically comes from the inclusion of hematite or other iron oxides during formation.
Uses & applications
Historically used for making stone tools (flintknapping); currently used in jewelry (cabochons), as decorative landscaping stones, and popular for rock tumbling.
Geological facts
Jasper has been used by humans for thousands of years; it was a favorite gem in the ancient world, mentioned in biblical texts and used in Babylonian seals.
Field identification & locations
Identify in the field by its smooth, waxy texture, inability to be scratched by a steel knife, and characteristic 'clinking' sound when struck against other hard rocks. Commonly found in riverbeds and glacial deposits.
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