sedimentary
Jasper (Red-Brown)
Silicon Dioxide (SiO2) with Iron Oxide impurities
Hardness: 6.5-7.0 (Mohs scale); Color: Dark reddish-brown to burnt sienna; Luster: Vitreous to waxy; Crystal Structure: Microcrystalline/Cryptocrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58-2.91.
- Hardness
- 6
- Color
- Dark reddish-brown to burnt sienna
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7.0 (Mohs scale); Color: Dark reddish-brown to burnt sienna; Luster: Vitreous to waxy; Crystal Structure: Microcrystalline/Cryptocrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58-2.91.
Formation & geological history
Forms primarily as a result of water-borne silica precipitation or through the replacement of organic materials. Often found in association with volcanogenic environments or sedimentary beds where mineral-rich water has permeated during various geological ages from Precambrian to recent periods.
Uses & applications
Commonly used as a gemstone for jewelry (cabochons, beads), decorative ornaments, and by lapidary hobbyists for stone tumbling. Historically used for making tools due to its hardness and sharp fracture edges.
Geological facts
The name 'Jasper' originated from the Greek word 'iaspis', meaning 'spotted stone'. It is a variety of chalcedony. Some ancients believed jasper could drive away evil spirits and protect against snake and spider bites.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a steel knife), smooth waxy feel when wet, and lack of visible grains. Commonly found in riverbeds, glacial deposits, and along coastlines. Tip for collectors: Look for high consistency in color and lack of deep cracks for better polishing results.
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