mineral

Chalcedony (Agate)

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Translucent white, tan, and reddish-brown; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Translucent white, tan, and reddish-brown
Luster: Waxy to vitreous

Identified June 19, 2026More mineral →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Translucent white, tan, and reddish-brown; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture).

Formation & geological history

Formed primarily in volcanic and sedimentary environments through the deposition of silica from groundwater into cavities (vugs) or fissures. Common in areas with ancient volcanic activity.

Uses & applications

Used extensively in jewelry as cabochons, in lapidary art, as precision bearings in mechanical instruments, and for industrial abrasives.

Geological facts

Agate is a variety of chalcedony characterized by its banding; it was often used by ancient civilizations for amulets and hardstone carving because of its durability.

Field identification & locations

Identify by its translucent edges when held to light, waxy texture, and lack of visible crystals. Often found in riverbeds or gravel pits in formerly volcanic regions.