sedimentary
Chert (Green Jasper)
Microcrystalline Quartz (SiO2) with iron silicate inclusions
Hardness: 6.5-7 on Mohs scale. Color: Olive green to brownish-green. Luster: Dull to waxy. Structure: Microcrystalline/Cryptocrystalline. Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Olive green to brownish-green
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Olive green to brownish-green. Luster: Dull to waxy. Structure: Microcrystalline/Cryptocrystalline. Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in marine environments. These specimens appear to be stream-tumbled river pebbles.
Uses & applications
Used historically for tool making (lithics); currently used for lapidary work, jewelry, and as decorative gravel.
Geological facts
Green Jasper is often associated with the presence of chlorite or iron silicate minerals. It was one of the first materials used by early humans for scrapers and projectile points due to its sharp conchoidal fracture.
Field identification & locations
Identify in the field by its hardness (will scratch glass), smooth waxy texture when wet, and lack of visible grains. Common in riverbeds and ancient sedimentary basins.
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