mineral

Chalcedony (Agate / Quartz Geode Fragment)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale. Color: Translucent milky white to pale yellowish-grey with iron-oxide staining. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.58-2.64.

Hardness: 6
Luster: Waxy to vitreous

Identified July 24, 2026More mineral →

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Physical properties

Formation & geological history

Forms at relatively low temperatures through the deposition of silica-rich hydrothermal fluids or groundwater filling cavities, vugs, or gas bubbles in volcanic or sedimentary rocks over thousands to millions of years.

Uses & applications

Used in lapidary arts for carving, tumbled stones, jewelry beads, and decorative mineral collection specimens. Industrially used historically for mortars and pestles due to hardness.

Geological facts

Chalcedony is composed of fine intergrowths of quartz and moganite. The hollow cavities (vugs) visible in this piece are characteristic of small geode formations or vesicular basalt cavities where silica precipitated.

Field identification & locations

Identified by its waxy luster, hardness (scratches glass, cannot be scratched by steel), translucent edges, and microcrystalline structure without distinct large crystal faces. Found worldwide in volcanic terrains, river beds, and desert gravels.