sedimentary
Jasper
Silicon Dioxide (SiO2) - Opaque Chalcedony
Hardness: 6.5-7 (Mohs); Color: Brown, tan, and gray-blue banding; Luster: Waxy to dull; Crystal Structure: Microcrystalline/Trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.5–2.9
- Hardness
- 6
- Color
- Brown, tan, and gray-blue banding
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Brown, tan, and gray-blue banding; Luster: Waxy to dull; Crystal Structure: Microcrystalline/Trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.5–2.9
Formation & geological history
Formed through the deposition of silica from water solutions or volcanic ash into sedimentary environments. This specific river-worn pebble was likely shaped by water erosion over thousands of years.
Uses & applications
Used primarily in lapidary work for making cabochons, beads, and ornamental carvings. Also common as aquarium gravel or decorative landscaping stones.
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 amulets since the Neolithic period.
Field identification & locations
Identify by its opacity (it does not transmit light even at the edges), smooth water-worn surface, and inability to be scratched by a steel knife. Commonly found in riverbeds and coastal regions globally.
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