sedimentary (silica-rich mineral variety)
Jasper (likely Lake Superior Jasper)
Silicon Dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 (Mohs scale); Color: Red, brown, and ochre with white or clear chalcedony bands; Luster: Dull to vitreous (waxy when polished); Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Red, brown, and ochre with white or clear chalcedony bands
- Luster
- Dull to vitreous (waxy when polished)
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Red, brown, and ochre with white or clear chalcedony bands; Luster: Dull to vitreous (waxy when polished); Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
Formation & geological history
Formed through the deposition of silica-rich fluids in cavities or volcanic gas bubbles, with significant iron oxidation creating the red coloring. These specimens are often related to the Midcontinent Rift System (approx. 1.1 billion years ago) and have been polished by glacial movement and water action.
Uses & applications
Commonly used in lapidary work for cabochons, beads, and ornamental stones. Also popular as a collector's pocket stone or used in rock tumbling.
Geological facts
Jasper is an opaque variety of chalcedony. The name 'jasper' comes from the Greek word 'iaspis', meaning 'spotted stone.' This specific rounded, water-worn shape suggests it was found in a gravel pit or a lake shore, such as the Great Lakes region.
Field identification & locations
Identify in the field by its opacity (unlike translucent agate), red/brown earthy tones, and high hardness (it will easily scratch glass). Common in river beds and glacial till in the Midwestern United States.
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Orbicular Jasper (Silicon Dioxide, SiO2)
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Red Jasper
Silicon Dioxide with Iron Oxide inclusions (SiO2 + Fe2O3)
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Green Jasper
Jasper (Silicon Dioxide, SiO2)
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