sedimentary
Yellow Chert or Jasper
Microcrystalline Quartz (SiO2) with iron oxide inclusions
Hardness: 6.5-7 on Mohs scale; Color: Dull yellow to mustard; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65.
- Hardness
- 6
- Color
- Dull yellow to mustard
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Dull yellow to mustard; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65.
Formation & geological history
Formed via the accumulation of silica-rich fluids in sedimentary environments or through the replacement of limestone. This specimen shows significant rounding from water erosion (fluvial or beach action).
Uses & applications
Used historically for stone tools due to sharp edges when fractured; modernly used for decorative landscaping, jewelry (if high quality), and as an abrasive.
Geological facts
Chert and jasper are among the oldest materials used by early humans for tools because of their hardness and predictable fracture patterns. Yellow hues are typically caused by goethite or limonite.
Field identification & locations
Identify in the field by its smooth, waxy surface when wet and its ability to scratch glass. Found globally in riverbeds, glacial tills, and coastal regions.
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