sedimentary
Chert (Red Jasper)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs). Color: Red, brownish-orange, dull to waxy luster. Crystal Structure: Hexagonal (cryptocrystalline). Opaque with a smooth, conchoidal fracture. Specific Gravity: 2.6-2.9.
- Hardness
- 6
- Color
- Red, brownish-orange, dull to waxy luster
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Physical properties
Hardness: 6.5-7 (Mohs). Color: Red, brownish-orange, dull to waxy luster. Crystal Structure: Hexagonal (cryptocrystalline). Opaque with a smooth, conchoidal fracture. Specific Gravity: 2.6-2.9.
Formation & geological history
Formed primarily as a chemical precipitate in seawater or through the replacement of limestone by silica-rich fluids. This specimen appears water-worn, potentially from a riverbed or shoreline. Range in age from Precambrian to Cenozoic.
Uses & applications
Used historically for stone tools due to sharp edges when fractured. Modernly used in lapidary work, jewelry (cabochons), and as a ground stone for landscaping or construction filler.
Geological facts
Red jasper is colored by iron inclusions (hematite). It has been used since antiquity for seals, amulets, and ornamentation, and was considered a protective stone by many ancient civilizations.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a steel nail), dull to waxy finish, and smooth, curved (conchoidal) chip marks. Often found in gravel deposits, riverbeds, and sedimentary basins worldwide.
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