sedimentary
Jasper
Silicon dioxide (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Dark green with brown/orange mottling; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None, conchoidal fracture.
- Hardness
- 6
- Color
- Dark green with brown/orange mottling
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Dark green with brown/orange mottling; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None, conchoidal fracture.
Formation & geological history
Formed from silica-rich precipitates in volcanic or sedimentary environments, often associated with hydrothermal activity. Iron and other impurities create the characteristic colors.
Uses & applications
Used in lapidary work for jewelry, cabochons, carvings, and as a collector's specimen.
Geological facts
Jasper is an opaque variety of chalcedony. The name 'Jasper' is derived from the Greek word 'iaspis', meaning spotted stone.
Field identification & locations
Identify in the field by its hardness (will scratch glass) and smooth, shell-like fracture pattern. Often found in riverbeds or coastal areas where erosion exposes volcanic deposits.
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