sedimentary
Chert Pebble (Jasper variety)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, brown, or yellowish-brown with white weathering rind; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- Tan, brown, or yellowish-brown with white weathering rind
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, brown, or yellowish-brown with white weathering rind; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in marine environments. This specimen has been water-worn and smoothed by alluvial or glacial transport, likely during the Holocene or Pleistocene epochs.
Uses & applications
Used historically for stone tools (flintknapping) due to its sharp edges. Modern uses include decorative landscaping, gravel production, and as a low-cost gemstone for tumbling/jewelry.
Geological facts
Chert is so durable that it often survives long-distance transport in riverbeds and on beaches while softer rocks erode away. Because of its hardness, it was once one of the most important minerals for human survival, used to create arrowheads and start fires.
Field identification & locations
Identify in the field by its waxy texture, smooth rounded surface, and the presence of 'half-moon' impact marks (chatter marks). Found globally in riverbeds, beaches, and gravel pits. Collectors should look for unique color patterns or translucent variants.
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