sedimentary

Agate (translucent water-worn pebble)

Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Brown, tan, white, and translucent; Luster: Waxy to vitreous (especially when wet); Structure: Microcrystalline; Cleavage: None/Conchoidal fracture.

Hardness: 6
Color: Brown, tan, white, and translucent
Luster: Waxy to vitreous (especially when wet)

Identified July 18, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brown, tan, white, and translucent; Luster: Waxy to vitreous (especially when wet); Structure: Microcrystalline; Cleavage: None/Conchoidal fracture.

Formation & geological history

Formed as secondary deposits in volcanic cavities or sedimentary pockets where silica-rich groundwater precipitates over time. This specimen is a water-worn river pebble, likely aged between 50 to 500 million years depending on the parent formation.

Uses & applications

Collecting, lapidary arts (polishing/tumbling), and occasionally used in jewelry or as decorative landscaping stone.

Geological facts

Agate is a variety of chalcedony characterized by its translucency and fine grain. When wet, the waxy luster and internal banding become much clearer to the naked eye.

Field identification & locations

Identify in the field by checking for translucency against a light source and a waxy texture. Commonly found in riverbeds, gravel pits, and ancient volcanic regions. Look for smooth, rounded edges and a shell-like (conchoidal) fracture pattern.