sedimentary
Jasper
Silicon dioxide (SiO2)
Hardness: 6.5-7 (Mohs). Color: Opaque yellow, brown, and ochre due to iron oxides (limonite). Luster: Dull to greasy (waxy when wet/polished). Crystal Structure: Hexagonal (microcrystalline/cryptocrystalline). Cleavage: None, conchoidal fracture.
- Hardness
- 6
- Luster
- Dull to greasy (waxy when wet/polished)
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Physical properties
Hardness: 6.5-7 (Mohs). Color: Opaque yellow, brown, and ochre due to iron oxides (limonite). Luster: Dull to greasy (waxy when wet/polished). Crystal Structure: Hexagonal (microcrystalline/cryptocrystalline). Cleavage: None, conchoidal fracture.
Formation & geological history
Formed through the accumulation of fine silica-rich materials, typically in sedimentary environments where volcanic ash or siliceous organisms are present. The colors are established as iron and other impurities permeate the silica during diagenesis.
Uses & applications
Commonly used for lapidary work, cabochons for jewelry, decorative carvings, and as dynamic landscaping material.
Geological facts
Jasper is an opaque variety of chalcedony. The name comes from the Greek word 'iaspis', meaning 'spotted stone.' It has been used since antiquity for seals and amulets.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a steel knife), opaque nature (unlike agate), and smooth, shell-like fracture surfaces. Often found in riverbeds or near volcanic deposits.
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