sedimentary
Yellow Chert Pebbles/Yellow Jasper
Microcrystalline Quartz (SiO2) with Goethite or Limonite inclusions
Hardness: 6.5-7 (Mohs), Color: Mustard yellow to golden brown, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.6-2.65
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs), Color: Mustard yellow to golden brown, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.6-2.65
Formation & geological history
Formed via the accumulation of silica-rich fluids in sedimentary environments or the replacement of limestone. Often found as water-worn pebbles in riverbeds or coastal deposits.
Uses & applications
Used for decorative landscaping, jewelry (as tumbled stones or cabochons), and historically for toolmaking (arrowheads/scrapers) due to its sharp conchoidal fracture.
Geological facts
Yellow coloring is typically caused by iron oxides. Chert is one of the most durable rocks, making it very common in gravel deposits worldwide.
Field identification & locations
Identify by its waxy luster, smoothness when water-worn, and inability to be scratched by a steel knife. Common in ancient river terraces and glacial till.
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