mineral

Agate Geode

Cryptocrystalline Quartz (SiO2) with Chalcedony banding

Hardness: 6.5-7 Mohs. Color: Blue-gray, white, and tan banding. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline). No cleavage. Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Blue-gray, white, and tan banding
Luster: Waxy to vitreous

Identified June 2, 2026More mineral →

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Physical properties

Hardness: 6.5-7 Mohs. Color: Blue-gray, white, and tan banding. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline). No cleavage. Specific Gravity: 2.58-2.64.

Formation & geological history

Formed within volcanic rock cavities (vesicles) where silica-rich groundwater deposited layers of chalcedony and quartz over millions of years.

Uses & applications

Commonly used for ornamental decorations, bookends, jewelry (cabochons), and as metaphysical healing stones.

Geological facts

The banding in agates is caused by rhythmic crystallization. This specimen shows 'water-line' agate, where flat layers indicate the orientation of gravity during formation.

Field identification & locations

Identified by concentric or horizontal banding and a translucent appearance when cut. Commonly found in Brazil, Uruguay, and the United States (Lake Superior/Oregon). Look for rounded nodules with a rough, 'cauliflower' exterior.

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