sedimentary
Jasper (Ferruginous Quartz)
Silicon Dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 (Mohs scale), Color: Reddish-brown, yellow, orange with dark streaks, Luster: Dull to waxy, Crystal Structure: Microcrystalline trigonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.58-2.91
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Reddish-brown, yellow, orange with dark streaks, Luster: Dull to waxy, Crystal Structure: Microcrystalline trigonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.58-2.91
Formation & geological history
Formed via the accumulation of silica in hydrothermic environments or sedimentary beds, often infused with iron oxides that provide the pigment. This specimen shows signs of fluvial or coastal tumbling, smoothing its edges over thousands of years.
Uses & applications
Commonly used in lapidary work for cabochons, beads, and tumbled stones. Also used as decorative stone in mosaics and historically for seals and amulets.
Geological facts
The name Jasper comes from the Greek word 'iaspis', meaning spotted stone. It is a dense, opaque variety of chalcedony. This specific cobble appears to be a river-worn or beach-worn stone, likely found in a glacial till or coastal deposit.
Field identification & locations
Identify by its hardness (cannot be scratched by a steel blade), opacity, and smooth, waxy feel when wet. Often found in riverbeds, or along rocky shorelines. Look for 'chert-like' fractures.
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