sedimentary
Green Chert (Jasper)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Hardness: 6.5-7 on Mohs scale; Color: Dull olive green; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Dull olive green
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Dull olive green; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); 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 by chemical precipitation in marine environments. Often found in nodules within limestone or as bedded deposits.
Uses & applications
Used historically for stone tools and arrowheads due to its sharp conchoidal fracture. Today used as a decorative stone, in lapidary work (cabochons), and as a collector's specimen.
Geological facts
Green chert is sometimes called 'Green Jasper' in the gemstone trade. Because of its extreme hardness and durability, it has been used by humans for millions of years to create cutting tools.
Field identification & locations
Identify in the field by its waxy luster, smoothness, and distinct shell-like (conchoidal) curves where broken. It cannot be easily scratched by a steel knife. Common in sedimentary basins worldwide.
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