mineral
Chalcedony (Agate) Pebble
Silicon Dioxide (SiO2)
Hardness: 6.5 - 7 on Mohs scale. Color: Translucent grayish-brown, yellowish-tan. Luster: Waxy to vitreous. Crystal system: Microcrystalline trigonal. Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Translucent grayish-brown, yellowish-tan
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5 - 7 on Mohs scale. Color: Translucent grayish-brown, yellowish-tan. Luster: Waxy to vitreous. Crystal system: Microcrystalline trigonal. Cleavage: None (conchoidal fracture).
Formation & geological history
Formed via secondary silica deposition in cavities of volcanic, sedimentary, or metamorphic rocks over millions of years, often rounded by river or beach water erosion.
Uses & applications
Used extensively for lapidary arts, jewelry, tumbled stones, decorative carvings, and mineral collections.
Geological facts
Chalcedony is composed of cryptocrystalline intergrowths of quartz and moganite. Its name is derived from the ancient Greek town of Chalcedon in Asia Minor.
Field identification & locations
Identified by its translucency, smooth water-worn surface, waxy luster, and lack of visible crystalline structures. Commonly found along riverbeds, gravel bars, and ocean beaches.
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