mineral

Agate (Polished Cabochon Slice)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Dark reddish-brown, brown, and translucent bands. Luster: Vitreous to waxy. Crystal Structure: Microcrystalline/Cryptocrystalline quartz. Cleavage: None, exhibits conchoidal fracture.

Hardness: 6
Color: Dark reddish-brown, brown, and translucent bands
Luster: Vitreous to waxy

Identified July 26, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary mineral in volcanic rock cavities (vesicles) where silica-rich groundwater deposited successive layers of microcrystalline quartz over millions of years.

Uses & applications

Polished for use as a gemstone in jewelry (cabochons, pendants), decorative ornamental carvings, and lapidary collections.

Geological facts

Agate is a microcrystalline variety of quartz known for its translucent properties and fine, colorful concentric banding pattern. Each agate pattern is unique to the cavity in which it formed.

Field identification & locations

Identified by its distinctive banding patterns, hardness, smooth glass-like feel, and translucent edges when backlit. Commonly found in riverbeds, gravel deposits, and ancient volcanic basalt flows globally, notably in Brazil, Uruguay, USA (Lake Superior), and Madagascar.

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