mineral

Banded Agate

Chalcedony (cryptocrystalline variety of Quartz), SiO2

Hardness: 6.5–7 on Mohs scale; Color: Red, orange, white, and translucent; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58–2.64

Hardness: 6
Color: Red, orange, white, and translucent
Luster: Waxy to vitreous

Identified May 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed primarily in volcanic rock cavities (vesicles) where silica-rich groundwater deposits successive layers of chalcedony over time. This specimen specifically resembles Lake Superior Agate, formed over 1 billion years ago during the Midcontinent Rift.

Uses & applications

Highly popular for jewelry (cabochons), lapidary arts, ornamental carving, and as a collector's gemstone. Historically used for making burnishing tools and pestles due to its hardness.

Geological facts

The banding in agates is caused by rhythmically repeated deposition of silica. This specific orange-red color is typically due to iron oxidation during the formation process.

Field identification & locations

Identify in the field by looking for 'fortification' banding patterns, a waxy texture, and light translucency when held to a torch. Common in glacial till, riverbeds, and gravel pits across the Upper Midwest USA.

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