sedimentary
Banded Jasper
Silicon Dioxide (SiO2) with impurities
Hardness: 6.5-7 (Mohs); Color: Red, grey, brown bands; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Conchoidal fracture; Specific gravity: 2.58-2.91
- Hardness
- 6
- Color
- Red, grey, brown bands
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Red, grey, brown bands; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Conchoidal fracture; Specific gravity: 2.58-2.91
Formation & geological history
Formed from the precipitation of silica from hot volcanic fluids or in sedimentary deposits where it replaces biological matter or fills cavities. The banding reflects intermittent deposition or chemical fluctuations during formation.
Uses & applications
Used primarily for lapidary work, jewelry (cabochons), as an ornamental stone in decor, and as a popular specimen for mineral collectors.
Geological facts
Jasper is an opaque variety of chalcedony. The red coloration is typically caused by iron inclusions (hematite). Ancient civilizations often used jasper for seals and amulets.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a knife), waxy to vitreous luster on fresh surfaces, and lack of cleavage. Found in riverbeds, volcanic regions, and sedimentary basins worldwide.
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