mineral

Banded Agate (Lake Superior Agate style)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs); Color: translucent orange, red, yellow, and brown; Luster: vitreous to waxy; Crystal Structure: Cryptocrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6

Hardness: 6
Color: translucent orange, red, yellow, and brown
Luster: vitreous to waxy

Identified July 5, 2026More mineral →

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Physical properties

Formation & geological history

Formed roughly 1.1 billion years ago during the Keweenawan Rift. Silica-rich groundwater deposited layers of quartz inside gas bubbles (vesicles) within volcanic basaltic lava flows.

Uses & applications

Used primarily for jewelry (cabochons), lapidary arts, decorative items, and highly sought after by mineral collectors.

Geological facts

The distinctive red and orange bands are caused by iron oxidation. One of the specimens in the image shows a small druzy pocket or 'geode' center with tiny quartz crystals.

Field identification & locations

Identify in the field by looking for translucent stones with concentric banding or a 'pitted' potato-like husk. Commonly found on beaches of Lake Superior and in glacial till throughout the Upper Midwest United States.

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