sedimentary
Yellow Chalcedony (Jasper/Chert Pebble)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Honey-yellow to brownish-gold; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 6
- Color
- Honey-yellow to brownish-gold
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Honey-yellow to brownish-gold; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the precipitation of silica-rich fluids in volcanic cavities or sedimentary environments. This specimen appears water-worn, indicating it was smoothed by abrasive action in a river or coastal environment over thousands of years.
Uses & applications
Used primarily for lapidary work (tumbled stones, beads, cabochons), grit in sandblasting (when crushed), and as a collector's item for hobbyists.
Geological facts
Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen even under a regular microscope. This specific oval shape is the result of natural erosion known as river-tumbling.
Field identification & locations
Identify in the field by its waxy appearance, smooth texture, and inability to be scratched by a steel knife. Common in gravel bars, river beds, and dry washes in volcanic or sedimentary regions.
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