sedimentary
Agate
Chalcedony (SiO2)
Hardness of 6.5-7 on the Mohs scale, colors vary widely due to impurities (grey, blue, white, red, brown), waxy to vitreous luster, microcrystalline (cryptocrystalline) quartz structure, conchoidal fracture with no true cleavage, specific gravity of 2.60-2.65.
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Physical properties
Hardness of 6.5-7 on the Mohs scale, colors vary widely due to impurities (grey, blue, white, red, brown), waxy to vitreous luster, microcrystalline (cryptocrystalline) quartz structure, conchoidal fracture with no true cleavage, specific gravity of 2.60-2.65.
Formation & geological history
Formed primarily within the cavities of volcanic rocks or ancient lavas through the deposition of silica-rich groundwater solutions in concentric layers over millions of years.
Uses & applications
Used for ornamental objects, polished display specimens, jewelry, lapidary arts, and historically for precision instruments like mortar and pestle sets.
Geological facts
Agate was named by Theophrastus, a Greek philosopher, after the Achates River in Sicily where these stones were first found in antiquity.
Field identification & locations
Identified by its distinctive banded or layered patterns, waxy luster, and translucent to opaque appearance. Commonly found worldwide in volcanic regions, riverbeds, and desert environments.
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