sedimentary
Chert (Green variety)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 6.5–7 (Mohs scale); Color: Olive to dull green; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.6–2.7
- Hardness
- 6
- Color
- Olive to dull green
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Olive to dull green; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.6–2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from silica-rich fluids in ocean floor marine environments; geological age varies widely from Precambrian to Cenozoic.
Uses & applications
Historically used for stone tools (arrowheads/scrapers) due to sharp edges; currently used for road gravel, decorative garden stones, and occasionally tumbled for low-cost jewelry or healing stone collections.
Geological facts
Green chert often gets its color from chlorite or reducing chemical environments during formation. It is extremely durable and can withstand millions of years of river transport, which explains its rounded, pebble-like appearance in this specimen.
Field identification & locations
Identify in the field by its smooth, waxy surface and its ability to scratch glass. It often occurs as nodules within limestone or as rounded river cobbles. Common globally in sedimentary basins.
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