gemstone

Agate

Silicon Dioxide (Chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, varied colors including brown, white, and amber, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture with no cleavage, specific gravity of 2.58 to 2.64.

Identified August 5, 2026More gemstone →

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

Formation & geological history

Formed mainly within cavities of volcanic and metamorphic rocks by the deposition of silica from groundwater solutions, often in concentric layers.

Uses & applications

Used for jewelry, ornamental carvings, decorative objects, and industrial bearings.

Geological facts

Agate is one of the most popular materials used in hardstone carving and was prized as a talisman in ancient civilizations.

Field identification & locations

Found worldwide, often in river gravels and volcanic rock cavities. Identify by its distinctive banding and translucent edges when held to light.

Other gemstone specimens

See all

Gemstone Ring

N/A - Set piece of jewelry, likely Amethyst or Garnet with Diamond or CZ

gemstone

Diamond and Gold Jewelry

Carbon (Diamond) / Au (Gold)

gemstone

Ammolite

Ammolite (Biogenic Aragonite with trace elements; fossils of Placenticeras meeki and Placenticeras intercalare)

mineral

Cubic Zirconia (simulant) or Diamond

ZrO2 (Cubic Zirconia) or C (Diamond)

gemstone

Red Jasper

Silicon Dioxide (SiO2) with Hematite inclusions

sedimentary

Black Opal Ring (Carved Opal)

Hydrated Silicon Dioxide (SiO2·nH2O)

gemstone