mineral

Banded Agate (Chert/Chaldcedony)

Silicon Dioxide (SiO₂)

Hardness: 6.5 - 7 (Mohs scale); Color: Layers of white, grey, brown, and orange (iron-stained); Luster: Waxy to vitreous; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.64

Hardness: 6
Color: Layers of white, grey, brown, and orange (iron-stained)
Luster: Waxy to vitreous

Identified March 26, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica from groundwater in cavities within igneous rocks or as nodules in sedimentary limestone. The banding represents different stages of mineral deposition over thousands of years.

Uses & applications

Predominantly used for lapidary work, jewelry (cabochons), ornamental carvings, and as a popular specimen for mineral collectors.

Geological facts

Agate is a variety of chalcedony. The distinct banding is caused by rhythmic crystallization often influenced by the presence of iron, manganese, or other metallic oxides which provide the coloring.

Field identification & locations

Identify in the field by its translucent edges, waxy appearance, and characteristic shell-like (conchoidal) fractures. Frequently found in riverbeds, glacial tills, or volcanic regions like the Lake Superior area or Brazil.

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