sedimentary

Agate

Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale. Color: Pale blue to white. Luster: Waxy to vitreous. Crystal structure: Hexagonal (microcrystalline). Cleavage: None, conchoidal fracture.

Hardness: 6
Color: Pale blue to white
Luster: Waxy to vitreous

Identified June 27, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Pale blue to white. Luster: Waxy to vitreous. Crystal structure: Hexagonal (microcrystalline). Cleavage: None, conchoidal fracture.

Formation & geological history

Forms when silica-rich groundwater fills cavities (vugs) in volcanic or sedimentary rocks. The silica precipitates in layers, often over millions of years, found in primary deposits or as secondary pebbles in rivers.

Uses & applications

Used extensively in jewelry (cabochons), precision weighs, mortar and pestles, and as a popular ornamental stone for collectors and lapidary artists.

Geological facts

Agate was named by the Greek philosopher Theophrastus who discovered the stone along the shore line of the river Achates in Sicily. No two agates are exactly alike in pattern or internal structure.

Field identification & locations

Identify by its characteristic banding (though sometimes subtle in small pieces), waxy texture, and translucency. Commonly found in riverbeds, lake shores, and gravel pits in volcanic regions.