mineral

Chalcedony (Agate)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs). Color: Waxy white to honey-yellow. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (hexagonal/monoclinic). Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Waxy white to honey-yellow
Luster: Waxy to vitreous

Identified July 16, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the precipitation of silica-rich groundwater in cavities of igneous rocks (basalts) or as nodules in sedimentary rocks. Geological age varies from recent to hundreds of millions of years.

Uses & applications

Used primarily in lapidary arts for jewelry, tumbled stones, and carvings. Historically used for making tools and seals due to its toughness.

Geological facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen without high magnification. This specific specimen shows a waxy luster and slight translucency typical of common chalcedony.

Field identification & locations

Identify in the field by its waxy appearance, smooth conchoidal fractures (glass-like break), and inability to be scratched by a steel knife. Common in riverbeds and volcanic regions.