mineral

Chalcedony (Agate Nodule)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Mohs hardness: 6.5 - 7; Color: translucent light grey to pale lavender blue with white microcrystalline banding; Luster: waxy to vitreous; Crystal structure: trigonal/microcrystalline aggregate; Cleavage: none; Conchoidal fracture.

Hardness: 6
Luster: waxy to vitreous

Identified July 26, 2026More mineral →

Explore Chalcedony (Agate Nodule) 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

Formed via secondary silica deposition from hydrothermal fluids precipitated within the gas cavities (vesicles) of volcanic rocks like basalt or rhyolite.

Uses & applications

Used extensively in gemstone lapidary, cabochon cutting, jewelry, ornamental carvings, and geological collections.

Geological facts

Chalcedony is a cryptocrystalline variety of quartz, meaning its crystals are too small to be seen without significant magnification. When featuring distinct concentric or fine banding, it is classified as agate.

Field identification & locations

Identified by its waxy luster, lack of distinct cleavage planes, translucent body, smooth conchoidal fracture, and ability to scratch glass easily. Commonly found in basaltic lava fields, desert gravels, and riverbeds worldwide.