sedimentary
Chert (Jasper variety)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: Dark brown to yellow-brown, Luster: Waxy to dull, Crystal structure: Microcrystalline (Trigonal system), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Dark brown to yellow-brown, Luster: Waxy to dull, Crystal structure: Microcrystalline (Trigonal system), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich microfossils or precipitation from silica-rich groundwater within sedimentary rock layers. This specimen shows signs of stream-tumbling/weathering which rounds the edges.
Uses & applications
Used ornamentally as gemstones, in decorative landscaping, and historically for making sharp tools like arrows and scrapers due to its conchoidal fracturing.
Geological facts
Chert and its variety Jasper were among the first resources used by early humans for tool-making because it breaks into razor-sharp edges. Its dense structure makes it very durable over geological time.
Field identification & locations
Identify in the field by its hardness (will scratch glass), waxy luster when broken, and lack of visible grains. Commonly found in riverbeds, glacial tills, and limestone deposits globally.
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