mineral
Agate (or Operculum / Fossil Shell)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 on Mohs scale; Color: Yellowish-brown, amber, tan with concentric banding; Luster: Waxy to vitreous; Crystal structure: Microcrystalline (trigonal); Cleavage: None, exhibits conchoidal fracture.
- Hardness
- 6
- Color
- Yellowish-brown, amber, tan with concentric banding
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Yellowish-brown, amber, tan with concentric banding; Luster: Waxy to vitreous; Crystal structure: Microcrystalline (trigonal); Cleavage: None, exhibits conchoidal fracture.
Formation & geological history
Formed through the deposition of silica from groundwater solution into cavities within igneous rocks or sedimentary host rocks, creating characteristic concentric bands.
Uses & applications
Used primarily in lapidary arts, jewelry making, decorative crafts, and as a popular collectible specimen.
Geological facts
Agates are famous for their unique, individual banding patterns. Some small disc-like, banded specimens found in rivers or beaches are nicknamed 'eye agates' or are sea snail operculums (trapdoors) petrified into chalcedony.
Field identification & locations
Look for distinct translucent concentric rings and a smooth, waxy surface when wet. Commonly found along gravel beds, riverbanks, lake shores, and beach deposits in volcanic terrains worldwide.
