sedimentary
Agate (translucent water-worn pebble)
Cryptocrystalline Quartz (SiO2)
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)
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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.
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