sedimentary
Jasper (Iron-stained Chert)
Silicon Dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 (Mohs scale); Color: Mottled orange, red, and off-white; Luster: Dull to waxy; Structure: Microcrystalline/Cryptocrystalline (cannot see crystals without a microscope); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9.
- Hardness
- 6
- Color
- Mottled orange, red, and off-white
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Mottled orange, red, and off-white; Luster: Dull to waxy; Structure: Microcrystalline/Cryptocrystalline (cannot see crystals without a microscope); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9.
Formation & geological history
Formed via the accumulation of silica in sedimentary environments, often through the replacement of other materials or as a chemical precipitate. The vibrant orange and red colors are caused by the presence of iron oxides (hematite/goethite). It can range from Precambrian to recent geological ages.
Uses & applications
Commonly used for lapidary work, jewelry (cabochons), interior decoration, and as a popular specimen for beginner rock collectors. Historically used for making tools due to its sharp conchoidal edges.
Geological facts
Jasper is a variety of chalcedony that is opaque. Ancient civilizations often used it for seals and protection talismans. Because it is so hard, it will easily scratch glass, which is a common test used by field researchers.
Field identification & locations
Identify in the field by its hardness (it cannot be scratched by a steel knife) and its smooth, shell-like fracture pattern. It is common across the globe, especially in the Western United States (Oregon, Idaho), Australia, and Brazil. Collectors should look for unique patterns or 'pictures' in the stone.
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