sedimentary
Jasper (Green Jasper/Chert)
Silicon Dioxide (SiO2)
Hardness: 6.5–7 on Mohs scale; Color: Dull green with beige and grey mottling; Luster: Waxy to vitreous; Structure: Cryptocrystalline (microscopic quartz crystals); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.91.
- Hardness
- 6
- Color
- Dull green with beige and grey mottling
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5–7 on Mohs scale; Color: Dull green with beige and grey mottling; Luster: Waxy to vitreous; Structure: Cryptocrystalline (microscopic quartz crystals); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.91.
Formation & geological history
Formed through the precipitation of silica from water, typically in sedimentary environments or as primary features in ocean floor deposits (bedded chert). This specimen appears water-worn, likely tumbled in a river or coastal environment over thousands of years.
Uses & applications
Used primarily for lapidary work, decorative carvings, and garden landscaping; historically used for stone tools and arrowheads due to its sharp conchoidal fracture.
Geological facts
Jasper is an opaque variety of chalcedony. The green color in specimens like this is often caused by inclusions of silicate minerals like chlorite or iron ores. It has been used as a gemstone since antiquity and was mentioned as a 'sacred stone' in various ancient civilizations.
Field identification & locations
Identify in the field by its hardness (it will scratch glass), its smooth waxy feel when wet, and the lack of visible crystal grains. Found worldwide in riverbeds and coastal regions, particularly in the Pacific Northwest (USA), India, and Brazil.
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