sedimentary
Chert (Yellow Jasper variant)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Tan to yellow-brown; Luster: Waxy to dull; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 6
- Color
- Tan to yellow-brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Tan to yellow-brown; Luster: Waxy to dull; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed via the accumulation of silica-rich organic remains (like radiolarians) or chemical precipitation from hydrothermal fluids within sedimentary layers. This river-worn cobble likely originated in the Paleozoic or Mesozoic era.
Uses & applications
Historically used for stone tools and flintknapping. Today used as decorative landscaping stone, in jewelry (as jasper), and as a gemstone for tumbling.
Geological facts
Chert is essentially the same mineral as flint, but the name ' jasper' is often applied to opaque, colorful varieties. It is extremely durable and can withstand millions of years of river transport.
Field identification & locations
Identify by its smooth, waxy texture and conchoidal (shell-like) fracture patterns. Highly resistant to scratching by steel. Common in riverbeds and glacial till throughout North America.
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