sedimentary
Chert (Jasper variety)
Silicon dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 on Mohs scale; Color: Tan, brown, and pink; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 6
- Color
- Tan, brown, and pink
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Tan, brown, and pink; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation in sedimentary environments. Can be found in various geological ages from Precambrian to Cenozoic.
Uses & applications
Used historically for stone tools and arrowheads; currently used for lapidary work, decorative landscaping, and as a polishing media.
Geological facts
This specimen features a distinct 'eye' or 'orb' pattern, likely caused by mineral replacement or a concretion during the formation phase. Chert is essentially a non-banded form of chalcedony.
Field identification & locations
Identify in the field by its smooth, waxy feel and characteristic curved (conchoidal) fractures. It will easily scratch glass. Found globally in limestone and dolomite beds.
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