sedimentary
Jasper (Chert)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 (Mohs); Color: Reddish-brown, earth tones with banding; Luster: Dull to waxy; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Reddish-brown, earth tones with banding
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Reddish-brown, earth tones with banding; Luster: Dull to waxy; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
Formation & geological history
Formed from the accumulation of silica-rich microfossils or precipitation from silica-rich fluids in sedimentary basins. Often associated with volcanic activity and hydrothermal precipitation.
Uses & applications
Used primarily in lapidary arts, jewelry (cabochons), interior decoration, and as a collectible specimen. Historically used for tools and weapons due to its sharp edges.
Geological facts
Jasper is an opaque variety of chalcedony. The name comes from the Greek word 'iaspis', meaning spotted stone. It has been used for seals and jewelry since the Minoan civilization.
Field identification & locations
Identify in the field by its hardness (will scratch glass), opaque nature, and smooth, curved (conchoidal) fracture surfaces. Commonly found in riverbeds, or as nodules in limestone and volcanic rock.
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