mineral
Chalcedony
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Translucent tan to yellowish-brown. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (hexagonal/trigonal). Cleavage: None. Specific gravity: 2.58-2.64.
- Hardness
- 6
- Color
- Translucent tan to yellowish-brown
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Translucent tan to yellowish-brown. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (hexagonal/trigonal). Cleavage: None. Specific gravity: 2.58-2.64.
Formation & geological history
Formed through the deposition of silica from aqueous solutions in volcanic and sedimentary environments, often filling cavities (vesicles) or cracks in rocks.
Uses & applications
Used primarily as semi-precious gemstones for jewelry (cabochons), ornamental carvings, and historically for stone tools due to its conchoidal fracture.
Geological facts
The name comes from the Latin 'chalcedonius', derived from the ancient seaport of Chalcedon in Asia Minor. It is actually a microcrystalline variety of quartz.
Field identification & locations
Identify by its waxy luster, translucency, and lack of visible crystals. Commonly found in riverbeds, deserts, and volcanic regions worldwide.
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Mineral/Rock
Banded Gneiss (River Rock/Pebble)
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Biotite Schist
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