mineral

Chalcedony (Common Opal variant or Agate pebble)

Silicon dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: Translucent white to milky cream, Luster: Waxy to vitreous, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal

Hardness: 6

Identified July 13, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Translucent white to milky cream, Luster: Waxy to vitreous, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal

Formation & geological history

Formed from the deposition of silica from groundwater in cavities of volcanic rocks or sedimentary formations over millions of years.

Uses & applications

Used in jewelry making as cabochons, for lapidary art, and popular among rock collectors for its smooth texture.

Geological facts

Chalcedony is composed of microscopic crystals of quartz and moganite. When it forms in concentric layers, it is called agate; when it is milky and lacks banding, it is simply common chalcedony.

Field identification & locations

Identify by its waxy luster, conchoidal fracture (smooth curved breaks), and ability to scratch glass. Commonly found in riverbeds, deserts, and volcanic regions worldwide.