mineral

Banded Agate (specifically Chalcedony nodule)

Agate (Silicon Dioxide, SiO2)

Hardness: 6.5–7 on Mohs scale. Color: Translucent orange, pink, and white bands. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.58–2.64.

Hardness: 6
Color: Translucent orange, pink, and white bands
Luster: Waxy to vitreous

Identified March 12, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the deposition of silica from groundwater in the cavities of igneous rocks such as basalt. Over millions of years, varying mineral impurities (like iron and manganese) create the distinct colorful banding.

Uses & applications

Predominantly used for lapidary work (cabochons), jewelry, ornamental carvings, and as a collector's specimen. Historically used for making mortars and pestles and hard-wearing burnishing tools.

Geological facts

Agate nodules often form inside volcanic gas bubbles called vesicles. This specimen shows 'water-level' or horizontal banding, indicating it remained stationary while the silica-rich fluids filled the cavity. Many agates are millions of years old, dating back to the Cenozoic or Mesozoic eras.

Field identification & locations

Identify in the field by its waxy luster, translucency when held to light, and distinctive concentric or horizontal color bands. Commonly found in riverbeds, shorelines, or areas with eroded volcanic soil such as the Great Lakes region or the American Southwest.

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