sedimentary

Yellow Chert (Chert / Jasper)

Silicon Dioxide (SiO2 / Microcrystalline Quartz)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Tan to yellow-brown; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 6
Color: Tan to yellow-brown
Luster: Dull to waxy

Identified June 25, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Tan to yellow-brown; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich fluids in sedimentary environments, often as nodules in limestone or as bedded deposits. This specimen appears water-worn, likely from a stream or river bed.

Uses & applications

Historically used for stone tools (arrowheads/scrapers) due to its sharp conchoidal fracture. Used today as decorative gravel, in lapidary work, and for casual mineral collecting.

Geological facts

Chert is so durable that it resists weathering better than surrounding rocks. Yellow-colored cherts often get their hue from small amounts of iron oxide (goethite) mixed within the silica.

Field identification & locations

Identify in the field by its smoothness, hardness (it will scratch glass), and its tendency to break with curved, shell-like surfaces. Found in riverbeds and limestone outcrops worldwide.