Banded Agate (with possible Chalcedony layers)

Physical Properties

Hardness: 6.5-7 on Mohs scale. Color: Multicolored bands including blue, tan, and reddish-brown. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline/cryptocrystalline quartz). Cleavage: None. Specific gravity: 2.58-2.64.

Formation & Geological History

Formed primarily in volcanic and metamorphic rocks as a secondary mineral through the deposition of silica from groundwater into cavities (vesicles) or cracks. The banding is caused by rhythmic crystallization cycles over thousands of years.

Uses & Applications

Used extensively in jewelry as gemstones (cabochons), ornamental carvings, bookends, and industrial mortars and pestles due to its hardness and resistance to chemicals.

Geological Facts

Agate was named by Theophrastus, a Greek philosopher, who discovered the stone along the shore line of the river Achates in modern-day Sicily. It is one of the oldest healing stones in history.

Field Identification & Locations

Identify by its characteristic colorful banding and waxy translucency. Common in the Lake Superior region (USA), Brazil, and Germany. Collectors look for sharp, high-contrast bands and unique color patterns.

Identified on: 5/14/2026

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