sedimentary
Jasper (Red/Green Brecciated)
Silicon Dioxide (SiO2) with iron oxide and chlorite inclusions
Hardness: 6.5-7 Mohs; Color: Mottled red, brown, and dull green; Luster: Vitreous to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9
- Hardness
- 6
- Color
- Mottled red, brown, and dull green
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 Mohs; Color: Mottled red, brown, and dull green; Luster: Vitreous to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9
Formation & geological history
Formed through the deposition of silica-rich fluids in cracks or volcanic cavities. Brecciated Jasper specifically forms when the original stone is fractured and then cemented back together by silica or hematite over millions of years.
Uses & applications
Used in the lapidary arts for cabochons, beads, and decorative carvings. It is also common as a landscape stone or a tumble-polished collector's item.
Geological facts
Jasper has been used since ancient times for amulets and tools; the name is derived from the Greek 'iaspis', meaning 'spotted stone.' It is a member of the chalcedony family.
Field identification & locations
Identify in the field by its high hardness (it cannot be scratched by a steel knife) and its smooth, waxy surface when wet. Commonly found in riverbeds, glacial tills, and desert pavements globally.
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