sedimentary
Jasper
Jasper (Silicon Dioxide, SiO2)
Hardness: 6.5–7 on Mohs scale; Color: Red, brown, or earthy tones (due to iron inclusions); Luster: Vitreous to greasy; Crystal structure: Microcrystalline (trigonal); Cleavage: None/Conchoidal fracture.
- Hardness
- 6
- Color
- Red, brown, or earthy tones (due to iron inclusions)
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 6.5–7 on Mohs scale; Color: Red, brown, or earthy tones (due to iron inclusions); Luster: Vitreous to greasy; Crystal structure: Microcrystalline (trigonal); Cleavage: None/Conchoidal fracture.
Formation & geological history
Formed through the process of silica enrichment in volcanic ash or fine-grained sediments. It originates from the interaction of hydrothermal fluids with minerals, often over millions of years.
Uses & applications
Used primarily in lapidary arts as gemstones for jewelry (cabochons), ornamental housewares, and historical tools (arrowheads). It is also highly valued by rockhounds and collectors.
Geological facts
Jasper is an impure variety of silica. The name 'Jasper' is derived from the Greek word 'iaspis', meaning 'spotted stone'. It was used in ancient times as a protection stone or for making seals.
Field identification & locations
Identify in the field by its opacity (unlike translucent chalcedony), smooth conchoidal fracture, and inability to be scratched by a steel pocket knife. Commonly found in riverbeds and volcanic deposits globally.
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