mineral
Chalcedony
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Brown, grey, white, or translucent. Luster: Waxy to vitreous. Crystal structure: Microcrystalline quartz (cryptocrystalline), trigonal system. Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.58-2.62.
- Hardness
- 6
- Color
- Brown, grey, white, or translucent
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Brown, grey, white, or translucent. Luster: Waxy to vitreous. Crystal structure: Microcrystalline quartz (cryptocrystalline), trigonal system. Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.58-2.62.
Formation & geological history
Forms in low-temperature aqueous environments, often filling cavities, vesicles, or fractures in volcanic and sedimentary rocks through the precipitation of silica-rich fluids.
Uses & applications
Used in ornamental carvings, gemstone cabochons, jewelry, and lapidary arts.
Geological facts
Chalcedony has been used since ancient times for making intricate seals, signet rings, and decorative objects. It serves as the parent material for many other gemstone varieties like agate, jasper, and onyx.
Field identification & locations
Identified by its waxy luster, conchoidal fracture, and microcrystalline structure. Found worldwide, particularly in volcanic regions and river gravels. Popular among rockhounds for tumbling and cabochon making.
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