mineral

Chalcedony (Tumbled Pebble)

Silicon Dioxide (SiO2)

Hardness: 6.5 - 7 on Mohs scale. Color: Translucent grayish-brown with reddish-iron inclusions. Luster: Vitreous to waxy. Crystal structure: Microcrystalline/Cryptocrystalline trigonal quartz. Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.58 - 2.64.

Hardness: 6
Color: Translucent grayish-brown with reddish-iron inclusions
Luster: Vitreous to waxy

Identified July 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed at low temperatures by precipitation from silica-rich groundwater within cavities and veins of volcanic, sedimentary, or metamorphic rocks over millions of years.

Uses & applications

Used in lapidary work, jewelry making, tumbled stone collections, healing crystals, and ornamental carvings.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its quartz crystals are too small to be seen without high magnification. It includes varieties such as agate, jasper, carnelian, and onyx.

Field identification & locations

Identify by its waxy luster, smooth tumbled texture, hardness (cannot be scratched by steel), and translucent nature under direct light. Commonly found in stream beds, volcanic gravels, and beaches worldwide.