mineral
Jasper (Green Jasper / Chert)
Silicon Dioxide (SiO2 with inclusions)
Mohs hardness: 6.5-7. Color: Olive green, yellowish-green, and brown swirls. Luster: Waxy to vitreous (glossy when wet/polished). Crystal structure: Microcrystalline/Cryptocrystalline (trigonal). Cleavage: None (conchoidal fracture). Specific gravity: 2.58-2.91.
- Hardness
- 6
- Color
- Olive green, yellowish-green, and brown swirls
- Luster
- Waxy to vitreous (glossy when wet/polished)
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Physical properties
Mohs hardness: 6.5-7. Color: Olive green, yellowish-green, and brown swirls. Luster: Waxy to vitreous (glossy when wet/polished). Crystal structure: Microcrystalline/Cryptocrystalline (trigonal). Cleavage: None (conchoidal fracture). Specific gravity: 2.58-2.91.
Formation & geological history
Formed through silica deposition in sedimentary or volcanic environments, often involving secondary hydrothermal alteration where microcrystalline quartz replaces organic or volcanic material while incorporating iron oxides and chlorite impurities that yield green coloration.
Uses & applications
Lapidary art, cabochons, polished decorative stones, tumbled rocks, and ornamental carvings.
Geological facts
Jasper is an opaque variety of chalcedony. Green jasper was highly prized in the ancient world, often used for cylinder seals, amulets, and ring stones in ancient Mesopotamia, Egypt, and Greece.
Field identification & locations
Look for a smooth, hard surface that cannot be scratched by a steel pocket knife. When wet, it shows a distinctive waxy sheen with swirl patterns or brecciated veinlets. Commonly found along riverbeds, gravel bars, and coastal beaches in volcanic regions.
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