sedimentary
Jasper
Silicon Dioxide (SiO2) with iron oxide impurities
Hardness: 6.5-7 on the Mohs scale. Color: Mottle red, brown, and yellow. Luster: Dull to vitreous/waxy. Crystal structure: Trigonal/Microcrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.58–2.91.
- Hardness
- 6
- Color
- Mottle red, brown, and yellow
- Luster
- Dull to vitreous/waxy
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Physical properties
Hardness: 6.5-7 on the Mohs scale. Color: Mottle red, brown, and yellow. Luster: Dull to vitreous/waxy. Crystal structure: Trigonal/Microcrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.58–2.91.
Formation & geological history
Formed through the deposition of silica from water-rich environments or via the replacement of organic material through petrification. Often associated with volcanic ash or sedimentary rocks. Geological age can range from hundreds of millions of years old to relatively modern.
Uses & applications
Predominantly used as a gemstone for jewelry (cabochons), lapidary art, and ornamental carvings. Historically used for making tools like scrapers due to its hardness and sharp fracture edges.
Geological facts
Jasper is an opaque variety of chalcedony. The name comes from the Greek word 'iaspis', meaning 'spotted stone.' It has been a popular gemstone since antiquity, mentioned in the Bible and highly valued by ancient Mesopotamian and Roman civilizations.
Field identification & locations
Identify in the field by its opacity (even on thin edges), its smooth 'waxy' texture when weathered by water, and its inability to be scratched by a steel knife. Commonly found in riverbeds, desert pavements, and coastal regions globally, especially in Oregon, Idaho, and Madagascar.
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