mineral

White Chalcedony (Agate)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Milky white to translucent blue-grey; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline/Trigonal (Cryptocrystalline quartz); Cleavage: None; Specific Gravity: 2.6

Hardness: 6
Color: Milky white to translucent blue-grey
Luster: Waxy to vitreous

Identified February 20, 2026More mineral →

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Physical properties

Formation & geological history

Formed by the precipitation of silica from groundwater in cavities (vesicles) of volcanic rocks or sedimentary environments. It can form over millions of years as silica-rich fluids cool or evaporate.

Uses & applications

Used widely in lapidary work for cabochons, beads, and carvings. Historically used for seals and cameos. Also used in industrial applications for its hardness and resistance to acids.

Geological facts

Chalcedony is a broad term that includes agate, jasper, and onyx. The term 'agate' specifically refers to chalcedony that shows banding, which is visible in this tumbled specimen. It has been used for jewelry for over 3,000 years, dating back to Bronze Age Crete.

Field identification & locations

Identify by its waxy luster, conchoidal fracture (if chipped), and translucent edges when held to light. Commonly found in riverbeds or volcanic regions like Brazil, India, and the Western United States. Collectors look for evenness of color or unique banding patterns.