Rock Identifier
Banded Agate (Sio2 (Silicon Dioxide / Chalcedony variety)) — mineral
mineral

Banded Agate

Sio2 (Silicon Dioxide / Chalcedony variety)

Hardness: 6.5-7 on Mohs scale. Color: Multicolored bands of grey, tan, white, and translucent brown. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Cleavage: None. Specific gravity: 2.58-2.64.

Hardness
6
Luster
Waxy to vitreous
Identified More mineral

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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Multicolored bands of grey, tan, white, and translucent brown. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Cleavage: None. Specific gravity: 2.58-2.64.

Formation & geological history

Formed primarily in volcanic and metamorphic rocks as silica-rich water fills cavities (vesicles). The banding represents different stages of mineral deposition over thousands of years. Usually found in ancient lava flows.

Uses & applications

Extensively used in lapidary arts for jewelry, handles for knives, bookends, and decorative coasters. Historically used for making mortars and pestles due to its hardness.

Geological facts

The name 'Agate' comes from the Achates River in Sicily where they were first found. Every agate is unique, and they are often considered one of the oldest healing stones in folklore.

Field identification & locations

Identify by looking for distinct parallel or concentric banding. To find in the field, look for nodules with a waxy luster when broken or sliced. Common in Brazil, Uruguay, and various locations across the United States.