sedimentary
Jasper (Iron-stained Chert)
Silicon Dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 (Mohs scale); Color: Dark brown to reddish-black with orange bands; Luster: Dull to waxy; Crystal Structure: Microcrystalline (Trigonal/Hexagonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.9
- Hardness
- 6
- Color
- Dark brown to reddish-black with orange bands
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Dark brown to reddish-black with orange bands; Luster: Dull to waxy; Crystal Structure: Microcrystalline (Trigonal/Hexagonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.9
Formation & geological history
Formed through the deposition of silica from water sources, often replacing organic material or filling cavities in volcanic and sedimentary rocks. This specimen likely contains hematite or goethite providing the dark coloration.
Uses & applications
Used primarily for lapidary work, jewelry (cabochons), river rock landscaping, and as a collector's specimen.
Geological facts
Jasper is an opaque variety of chalcedony. The name comes from the Greek word 'iaspis', meaning spotted stone. It has been used for seals and amulets since the Minoan civilization.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a steel knife), opaque nature, and smooth, rounded surface indicating river or beach tumbling. Found in gravel beds, shorelines, and ancient volcanic outcrops.
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