sedimentary

Agate

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Banded shades of tan, white, brown, and red; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (Microcrystalline Quartz); Translucent to opaque.

Hardness: 6
Color: Banded shades of tan, white, brown, and red
Luster: Waxy to vitreous

Identified July 4, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Banded shades of tan, white, brown, and red; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (Microcrystalline Quartz); Translucent to opaque.

Formation & geological history

Formed primarily in volcanic rock cavities (vugs) or certain sedimentary formations by the deposition of silica from groundwater. The bands represent different stages of mineral deposition over thousands of years.

Uses & applications

Used widely in lapidary arts for jewelry, as ornamental stones, in precision pendulums, and historically for mortars and pestles due to its hardness.

Geological facts

Agate is named after the Achates River in Sicily where it was first discovered. No two agates are exactly alike, making each specimen unique. This specific specimen appears to be a water-worn river pebble.

Field identification & locations

Identify by its waxy luster, variety of colors, and characteristic concentric or moss-like banding. Common in riverbeds, gravel pits, and ancient volcanic regions worldwide.