mineral

Chalcedony nodule (possibly agate)

Microcrystalline quartz, SiO₂; potentially banded agate

AI-generated identification · may be incorrect

Small rounded, partly translucent gray-blue nodule with a waxy to glassy luster and a darker crystalline-looking cavity or inclusion. Quartz hardness is 6.5–7 Mohs, with no obvious cleavage and conchoidal fracture; specific gravity is about 2.6.

Identified September 18, 2026More mineral →

Explore Chalcedony nodule (possibly agate) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Likely formed when silica-rich groundwater filled a vesicle or cavity in volcanic rock, depositing chalcedony and possibly later quartz crystals. Such nodules commonly formed during the Cenozoic or older volcanic episodes, but age cannot be determined from the photograph.

Uses & applications

Used for cabochons, beads, carvings, tumbling, and ornamental specimens; industrial chalcedony is a minor silica source.

Geological facts

The translucent outer material is consistent with chalcedony, while the darker center may be druzy quartz, another mineral inclusion, or simply a cavity shadow.

Field identification & locations

Identify by translucency, waxy appearance, hardness, and conchoidal fracture; it should scratch glass but not be scratched by a steel knife. Common in volcanic terrains and gravel deposits worldwide.