mineral

Agate

Agate (Cryptocrystalline variety of Quartz, SiO2)

Hardness: 6.5-7 Mohs; Color: Grey, lavender, and white bands; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None; Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Grey, lavender, and white bands
Luster: Waxy to vitreous

Identified June 27, 2026More mineral →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Grey, lavender, and white bands; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None; Specific Gravity: 2.58-2.64.

Formation & geological history

Formed in volcanic rock cavities (vesicles) where silica-rich groundwater deposited microscopic quartz crystals in layers over time. Typical ages range from millions to hundreds of millions of years.

Uses & applications

Commonly used in jewelry (cabochons), ornamental carvings, bookends, and industrial mortars and pestles due to its hardness and chemical resistance.

Geological facts

Agate is named after the Achates River in Sicily. The 'fortification' pattern seen here consists of concentric bands that resemble the layout of ancient defensive walls.

Field identification & locations

Identify by its waxy luster on fractured surfaces and distinct concentric banding. Often found in riverbeds or areas with weathered volcanic rock. Collectors look for clarity and unique patterns.

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Mineral/Rock

Banded Gneiss (River Rock/Pebble)

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Metamorphic Rock

Green Apatite on Albite

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mineral