sedimentary
Chert (Jasper variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: reddish-brown to tan; Luster: dull to waxy; Structure: cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 6
- Color
- reddish-brown to tan
- Luster
- dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: reddish-brown to tan; Luster: dull to waxy; Structure: cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation from silica-rich fluids within sedimentary rock layers. Most common in ancient marine environments.
Uses & applications
Historically used for stone tools (knapping); today used in landscaping, decorative stone, and lapidary arts for jewelry and tumbling.
Geological facts
Chert is so hard it can strike sparks from steel. Specimens with vibrant red coloring due to iron inclusions are specifically referred to as Jasper.
Field identification & locations
Identify in the field by its smooth, waxy feel and shell-like (conchoidal) fracture patterns. Frequently found in stream beds or within limestone and dolomite formations.
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