mineral
Chalcedony (Agate / Quartz Nodule)
Silicon Dioxide (SiO2)
Hardness of 6.5-7 on Mohs scale; waxy to vitreous luster; microcrystalline/cryptocrystalline quartz structure; translucent pale yellow to yellowish-brown coloration; conchoidal fracture.
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Physical properties
Hardness of 6.5-7 on Mohs scale; waxy to vitreous luster; microcrystalline/cryptocrystalline quartz structure; translucent pale yellow to yellowish-brown coloration; conchoidal fracture.
Formation & geological history
Formed through the deposition of silica-rich water solutions within cavities of volcanic rocks or sedimentary formations over millions of years.
Uses & applications
Popular for lapidary work, jewelry, cabochons, tumbling, ornamental carvings, and geological collections.
Geological facts
Chalcedony has been used by humans for thousands of years to craft tools, arrowheads, and seals due to its predictable conchoidal fracture and hardness.
Field identification & locations
Look for a smooth, waxy surface with semi-translucent yellow-brown hues embedded in beach pebbles or basalt hosts. Commonly found along rocky coastlines and riverbeds.
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