sedimentary
Chert (Jasper variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown and grey mottled; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 6
- Color
- Reddish-brown and grey mottled
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown and grey mottled; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation from fluids within sedimentary rock layers. This specimen shows signs of stream-tumbling, smoothing its rough edges over time.
Uses & applications
Historically used for stone tools due to sharp edges; currently used for lapidary work, jewelry, and as decorative landscaping stone.
Geological facts
Chert is so durable that it often survives long after the surrounding rock has weathered away. Red varieties containing iron oxide inclusions are specifically called Jasper.
Field identification & locations
Identify by its waxy luster, hardness (it will scratch glass), and distinctive shell-like (conchoidal) fracture patterns. Frequently found in riverbeds, gravel pits, and coastal areas.
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