sedimentary
Jasper (Banded Jasper)
Silicon Dioxide (SiO2) with impurities
Hardness: 6.5–7 (Mohs scale); Color: Brown, tan, cream, and grey bands; Luster: Vitreous to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.91
- Hardness
- 6
- Color
- Brown, tan, cream, and grey bands
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Brown, tan, cream, and grey bands; Luster: Vitreous to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.91
Formation & geological history
Formed through the deposition of silica from mineral-rich waters in sedimentary environments, often associated with volcanic ash or iron-rich deposits. This specimen likely dates from the Precambrian to Cenozoic eras.
Uses & applications
Used primarily in lapidary work, jewelry (cabochons and beads), ornamental carvings, and as a popular collector's item due to its unique banding patterns.
Geological facts
Jasper is an opaque variety of chalcedony. The banding in 'picture jasper' or 'banded jasper' is often caused by flows of mineralized water or wind-deposited layers of ash that were later petrified by silica.
Field identification & locations
Identify by its hardness (it can scratch glass) and its opaque, smooth surface when tumbled. It is commonly found in riverbeds, deserts, and volcanic regions globally, notably in the Western USA, Brazil, and India.
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