gemstone

White Agate / Chalcedony

Silicon Dioxide (SiO2)

Hardness of 6.5 to 7 on the Mohs scale, milky white to translucent color, waxy to vitreous luster, microcrystalline (cryptocrystalline) quartz structure, conchoidal fracture with no true cleavage, and a specific gravity of 2.60 to 2.65.

Identified July 31, 2026More gemstone →

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Physical properties

Formation & geological history

Forms primarily from silica-rich groundwater solutions depositing silica in cavities, vesicles, or fractures of igneous, sedimentary, or metamorphic rocks over millions of years.

Uses & applications

Used widely in ornamental carvings, cabochons, beaded jewelry, tumbling, and as a collector specimen.

Geological facts

Agate has been used since antiquity (such as in Ancient Greece and Egypt) for signet rings, seals, and protective amulets due to its durability and fine polishing ability.

Field identification & locations

Easily identified by its smooth, water-worn texture, conchoidal luster, lack of cleavage, and translucent milky appearance when held to the light. Commonly found in riverbeds, glacial drift, and volcanic regions worldwide.