mineral
Chalcedony (Carnelian / Agate)
Silicon Dioxide (SiO2)
Hardness 6.5-7 on Mohs scale; waxy to vitreous luster; microcrystalline/cryptocrystalline trigonal structure; translucent yellowish-brown to amber color; smooth conchoidal fracture.
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Physical properties
Hardness 6.5-7 on Mohs scale; waxy to vitreous luster; microcrystalline/cryptocrystalline trigonal structure; translucent yellowish-brown to amber color; smooth conchoidal fracture.
Formation & geological history
Formed through the deposition of silica-rich fluids in cavities and fissures of volcanic or sedimentary rocks at low temperatures.
Uses & applications
Used widely for semi-precious jewelry, lapidary art, carvings, beads, and as a popular collectible gemstone.
Geological facts
Carnelian and yellow chalcedony have been used for millennia, dating back to ancient Minoan, Egyptian, and Roman signet rings and amulets due to their durability and polish.
Field identification & locations
Look for a translucent, waxy stone with rounded edges and sub-conchoidal fractures. Commonly found along gravel beds, riverbanks, and volcanic beaches globally (e.g., Brazil, India, Oregon, Washington, Madagascar).
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