sedimentary
Chert (Green Chert or Jasper)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs); Color: Olive-green to brownish-green; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoïdal fracture); Specific Gravity: 2.6 - 2.7
- Hardness
- 6
- Color
- Olive-green to brownish-green
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Olive-green to brownish-green; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoïdal fracture); Specific Gravity: 2.6 - 2.7
Formation & geological history
Formed by the accumulation of siliceous remains of microscopic organisms (like diatoms or radiolarians) or through chemical precipitation in marine environments. It often occurs as nodules or layers within limestone or shale.
Uses & applications
Used historically for stone tools due to its conchoïdal fracture; currently used for decorative gravel, landscaping, and as a semi-precious gemstone in tumbling or lapidary work.
Geological facts
This specimen appears water-worn and tumbled, likely found in a riverbed or coastal area. Green varieties are often called 'Green Jasper' in the gemstone trade if they are opaque enough.
Field identification & locations
Identify in the field by its smooth, waxy feel, hardness (will scratch glass), and its characteristic shell-like (conchoïdal) curved break patterns. Found globally in sedimentary basins.
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