sedimentary
Yellow Jasper
Silicon Dioxide (SiO2) with iron oxide impurities
Hardness: 6.5–7 (Mohs scale); Color: Mustardy yellow to golden brown with iron-rich dark veins; Luster: Dull to waxy; Crystal Structure: Microcrystalline/Cryptocrystalline (Trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.5–2.9
- Hardness
- 6
- Color
- Mustardy yellow to golden brown with iron-rich dark veins
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Mustardy yellow to golden brown with iron-rich dark veins; Luster: Dull to waxy; Crystal Structure: Microcrystalline/Cryptocrystalline (Trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.5–2.9
Formation & geological history
Formed through the accumulation of silica-rich fluids in volcanic ash or sedimentary deposits, often during the Cretaceous or Jurassic periods. The yellow hue comes from goethite or other hydrous iron oxides during the silicification process.
Uses & applications
Commonly used in the lapidary arts for cabochons, beads, and tumbled stones. Historically used for ornaments, amulets, and architectural inlays. In industry, it can be used for mortar and pestles due to its hardness.
Geological facts
Jasper has been used by humans for thousands of years; it was a favorite in the ancient world for cylinder seals and amulets. Yellow Jasper is specifically associated with solar energy in many folklore traditions.
Field identification & locations
Identify in the field by its opaque nature (unlike translucent chalcedony), yellow-tan 'mustard' color, and the fact that it cannot be scratched by a steel knife. It is frequently found in riverbeds or coastal deposits. Significant locations include South Africa, India, and the Western USA.
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