sedimentary
Jasper (Iron-stained Quartzite/Chert)
Silicon Dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 (Mohs scale); Color: Brownish-red to tan; Luster: Dull to waxy; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9
- Hardness
- 6
- Color
- Brownish-red to tan
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Brownish-red to tan; Luster: Dull to waxy; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9
Formation & geological history
Formed from the precipitation of silica in or between sedimentary layers, often influenced by hydrothermal activity. This specimen shows significant rounding from alluvial/fluvial processes (water erosion).
Uses & applications
Commonly used for lapidary work (cabochons), river rock landscaping, and as a decorative stone for aquarium or home decor.
Geological facts
The reddish-brown hue is caused by the oxidation of iron within the silica matrix. Jasper has been used since antiquity for seal stones and amulets due to its durability and ability to take a high polish.
Field identification & locations
Identify in the field by its hardness (it will scratch glass), its smooth, waxy surface when wet, and the lack of visible crystal grains. Found frequently in riverbeds and glacial tills.
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