sedimentary
Yellow Jasper (Chert variant)
Silicon Dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 on Mohs scale; Color: Mustard yellow to golden brown with iron staining; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Opaque.
- Hardness
- 6
- Color
- Mustard yellow to golden brown with iron staining
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Mustard yellow to golden brown with iron staining; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Opaque.
Formation & geological history
Formed from the precipitation of silica in sedimentary environments, often associated with ancient sea beds or volcanic ash deposits where hydrothermal activity circulates silica-rich fluids through the substrate.
Uses & applications
Primarily used as a lapidary material for cabochons, beads, and decorative carvings. Industrially used in abrasive applications due to its hardness.
Geological facts
Yellow jasper has been used since antiquity for ornaments and talismans. Its yellow hue is caused by high concentrations of goethite or limonite (iron hydroxides) within the quartz matrix.
Field identification & locations
Look for a smooth, waxy surface on weathered river stones that cannot be scratched by a steel knife. It is frequently found in riverbeds, glacial till, and coastal areas across the United States, Egypt, and Brazil.
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