mineral

Agate

Cryptocrystalline Silicon Dioxide (SiO2)

Hardness: 6.5-7. Color: Brown, tan, and translucent. Luster: Vitreous to waxy. Crystal Structure: Hexagonal (cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Brown, tan, and translucent
Luster: Vitreous to waxy

Identified June 30, 2026More mineral →

Explore Agate in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 6.5-7. Color: Brown, tan, and translucent. Luster: Vitreous to waxy. Crystal Structure: Hexagonal (cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.64.

Formation & geological history

Formed as a secondary mineral in volcanic rock cavities (vesicles) or sedimentary deposits. Silica-rich groundwater precipitates layers of microscopic quartz crystals over long periods.

Uses & applications

Used in lapidary arts, jewelry (cabochons), burnishing tools, and as ornamental collection pieces. It also has historical industrial use in precision balances and mortars.

Geological facts

Agate is a variety of chalcedony distinguished by its banding or translucency. It has been used in jewelry since the Neolithic era and was popular in Ancient Greece for amulets.

Field identification & locations

Identify in the field by its translucency (light can pass through edges), waxy texture when wet, and lack of visible grains. Common in river beds, beaches, and volcanic regions.