mineral

Chalcedony (Botryoidal/Agate nodule)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Translucent white to milky gray. Luster: Waxy to vitreous. Crystal structure: Trigonal/Monoclinic (microscopic). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6.

Hardness: 6
Color: Translucent white to milky gray
Luster: Waxy to vitreous

Identified March 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed by the precipitation of silica from groundwater in cavities or veins within volcanic or sedimentary rocks. This specimen likely formed as a 'pocket' or vesicle filling. Geological age can range from Cenozoic to Precambrian depending on the host rock.

Uses & applications

Used primarily in lapidary work for cabochons, beads, and carvings. High-quality translucent pieces are used in jewelry and by mineral collectors for their unique 'bubbly' botryoidal texture.

Geological facts

Chalcedony is technically a fibrous variety of quartz. When it exhibits banding, it is called Agate. In ancient times, it was used to create seals and amulets because wax does not stick to it.

Field identification & locations

Identify in the field by its waxy luster, smooth rounded surfaces (botryoidal growth), and inability to be scratched by a steel knife. Commonly found in riverbeds, desert washes, and near volcanic outcroppings in Oregon, Arizona, and Brazil.

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