sedimentary
Chert / Jasper Pebble
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: yellowish-tan, brown, reddish-orange, and grey earth tones; Luster: waxy to dull; Fracture: conchoidal; Specific Gravity: ~2.65
- Hardness
- 6
- Color
- yellowish-tan, brown, reddish-orange, and grey earth tones
- Luster
- waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: yellowish-tan, brown, reddish-orange, and grey earth tones; Luster: waxy to dull; Fracture: conchoidal; Specific Gravity: ~2.65
Formation & geological history
Formed via the accumulation of microcrystalline silica derived from biogenic radiolarian or diatomaceous remains, or chemical precipitation, often weathered and rounded in riverbeds or marine shorelines.
Uses & applications
Historically used for knapping stone tools (arrowheads, scrapers) and starting fires; currently used for lapidary work, decorative landscaping, and casual collecting.
Geological facts
Chert and jasper are dense, fine-grained silica rocks. The iron oxide impurities give this specimen its characteristic warm yellow-brown hues.
Field identification & locations
Identified by its high hardness (scratches glass, cannot be scratched by a steel nail), waxy luster, smooth weathered surfaces, and conchoidal fracturing. Found widely in stream beds, gravel pits, and sedimentary formations.
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