sedimentary

Banded Agate

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 Mohs; Color: Brown, tan, and white; Luster: Waxy to vitreous; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64

Hardness: 6
Color: Brown, tan, and white
Luster: Waxy to vitreous

Identified July 3, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brown, tan, and white; Luster: Waxy to vitreous; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64

Formation & geological history

Formed by the deposition of silica from groundwater into cavities (vesicles) of igneous or sedimentary rocks. The banding represents different stages of mineral deposition over time.

Uses & applications

Commonly used for jewelry (cabochons), ornamental carvings, tumbling, and decorative stones. Historically used for hardstone carvings and precision mechanical parts.

Geological facts

The banding in agate is caused by the rhythmic precipitation of silica. Every layer represents a unique chemical change in the fluid that filled the stone's cavity millions of years ago.

Field identification & locations

Identified by concentric or parallel banding and a waxy surface when broken. Commonly found in riverbeds, lake shores (like Lake Superior), and volcanic areas. Look for translucent edges when held to light.