sedimentary
Agate (Water-Worn)
Cryptocrystalline quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Honey-yellow, translucent to opaque; Luster: Waxy to vitreous; Structure: Microcrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6
- Hardness
- 6
- Color
- Honey-yellow, translucent to opaque
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 Mohs; Color: Honey-yellow, translucent to opaque; Luster: Waxy to vitreous; Structure: Microcrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6
Formation & geological history
Formed from silica-rich groundwater filling voids (gas bubbles) in volcanic rock or cavities in sedimentary rock. This specific specimen has been smoothed and rounded by river or tidal action over thousands of years.
Uses & applications
Used for jewelry (lapidary), decorative ornaments, collection, and historically for burnishing tools or mortar and pestles due to its hardness.
Geological facts
This specimen exhibits a 'crazed' or frosted surface texture common in river agates or sea glass, which results from long-term exposure to water and varying temperatures. Agates are the state rock of many locations including Oregon, Minnesota, and Kentucky.
Field identification & locations
Identify in the field by checking for translucency (candling with a flashlight) and search for the characteristic 'waxy' texture. Commonly found in riverbeds, gravel bars, and coastlines near volcanic regions.
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