Mineral

Agate

SiO2 (Silicon dioxide, chalcedony variety)

Hardness: 6.5-7 (Mohs), Color: Translucent to opaque, often banded, varying colors including orange, white, and red in this specimen. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Cleavage: None.

Hardness: 6
Luster: Waxy to vitreous

Identified June 17, 2026More mineral →

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Physical properties

Formation & geological history

Forms in volcanic rocks or ancient lavas as nodules or geodes, formed by the deposition of silica from groundwater in cavities.

Uses & applications

Used primarily in jewelry, ornamental objects, carving, and as a collector's stone. Also used historically for hardstone carving.

Geological facts

Agate is a variety of chalcedony characterized by its fineness of grain and brightness of color. It was highly valued in antiquity as a talisman or amulet.

Field identification & locations

Identify by its waxy luster, hardness (scratches glass), and often banded appearance. Translucency is a key feature separating it from jasper. Commonly found worldwide, especially in Brazil, Uruguay, and parts of the US (like Lake Superior agate).