sedimentary
Jasper (Iron-stained)
Jasper (Silicon Dioxide, SiO₂ with Iron inclusions)
Hardness: 6.5-7 (Mohs), Color: brownish-red to yellow (limonite/hematite staining), Luster: dull to waxy, Crystal structure: cryptocrystalline microquartz, Cleavage: none (conchoidal fracture), Specific Gravity: 2.58-2.91.
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs), Color: brownish-red to yellow (limonite/hematite staining), Luster: dull to waxy, Crystal structure: cryptocrystalline microquartz, Cleavage: none (conchoidal fracture), Specific Gravity: 2.58-2.91.
Formation & geological history
Formed through the infiltration of silica in sedimentary environments or volcanic ash; the characteristic colors come from impurities of iron oxides. Most jasper dates from the Precambrian to Cenozoic eras.
Uses & applications
Primarily used for lapidary work, decorative carvings, jewelry (cabochons), and as a collector's specimen. Historically used for making tools and seals.
Geological facts
The name 'Jasper' is derived from the Greek for 'spotted stone'. It is an opaque variety of chalcedony. Some specimens are so rich in iron they are considered iron ore.
Field identification & locations
Identify by its hardness (cannot be scratched by a steel knife), opacity, and smooth feel when wet. Found commonly in riverbeds, coastal gravels, and deserts globally.
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