sedimentary
Chert (Jasper variety)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Yellowish-brown, tan, with darker stripes; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline quartz; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Yellowish-brown, tan, with darker stripes
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Yellowish-brown, tan, with darker stripes; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline quartz; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation of silica in marine or groundwater environments. This specimen appears as a water-worn pebble, likely from a river or glacial deposit.
Uses & applications
Used historically for stone tools due to sharp edges; currently used for lapidary work, jewelry (beads/cabochons), and as aquarium or decorative stone.
Geological facts
Chert is so durable that it can survive long-distance transport in rivers and glacial till. High-quality colored chert is often referred to as Jasper.
Field identification & locations
Identify by its hardness (cannot be scratched by a steel knife) and its smooth, waxy texture. Commonly found in gravel pits, river beds, and coastal erosion zones.
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