mineral

Agate (Chalcedony)

Cryptocrystalline Silica or Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs); Color: Translucent white with orange-brown iron staining and subtle banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microscopic); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.58-2.64.

Hardness: 6
Luster: Waxy to vitreous

Identified May 9, 2026More mineral →

Explore Agate (Chalcedony) 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 in cavities (geodes/vugs) within volcanic rock or ancient sedimentary formations where silica-rich groundwater deposits layers of quartz over time. This specimen likely dates from the Tertiary to Cretaceous periods.

Uses & applications

Extensively used for semi-precious jewelry, ornamental carvings, high-grade abrasive tools, and laboratory mortar and pestles due to its hardness and resistance to chemicals.

Geological facts

The banding in agates is caused by the rhythmic precipitation of silica. No two agates are exactly alike, making them a favorite for collectors. The orange coloring is often due to iron oxide impurities (limonite or hematite).

Field identification & locations

Identified in the field by its waxy luster, conchoidal (shell-like) fracture, and degree of translucency. Commonly found in riverbeds, beaches, and areas with historical volcanic activity.