mineral

White Chalcedony (Agate)

Silicon Dioxide (SiO2)

Hardness: 6.5–7 on the Mohs scale. Color: Milky white to translucent grey. Luster: Waxy to vitreous. Crystal Structure: Hexagonal/Trigonal (microcrystalline/cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.60–2.64.

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

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica from groundwater in cavities of volcanic igneous rocks or sedimentary strata. It often precipitates at relatively low temperatures.

Uses & applications

Primary uses include gemstones, ornamental carvings, cabochons for jewelry, and historically for tools such as scrapers and arrowheads due to its hardness and fracture pattern.

Geological facts

In ancient times, chalcedony was used to make seals because wax would not stick to it. The name is derived from the ancient Greek town of Chalcedon in Asia Minor.

Field identification & locations

Identify in the field by its waxy appearance, lack of visible crystals, and conchoidal (shell-like) fracture. Commonly found in Brazil, India, Madagascar, and the USA (Oregon, Arizona). Its durability makes it easy for collectors to identify even in riverbeds.