mineral

Polished banded agate or jasper nodule

Microcrystalline quartz (chalcedony), SiO₂, possibly iron-oxide-rich jasper

AI-generated identification · may be incorrect

Concentric cream, tan, gray, and brown banding with a waxy to dull luster; likely hardness about 6.5–7 Mohs, no obvious cleavage, and cryptocrystalline quartz structure. The central pale area may be a druzy or quartz-filled cavity.

Identified August 21, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, depositing successive chalcedony layers; iron oxides create the brown and red colors. Such nodules commonly formed during the Cenozoic or older volcanic episodes, but the specimen’s exact age cannot be determined visually.

Uses & applications

Used as ornamental stone, cabochons, carvings, beads, and tumbling material; attractive patterned pieces are collected and occasionally used in jewelry.

Geological facts

The visible curved layers are typical of fortification agate, while more opaque layers may be called jasper. A glassy crystal-lined pocket would support an agate identification.

Field identification & locations

Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States. Check for a glassy quartz-like fracture, hardness greater than steel, and banding continuing through a freshly cut surface; dyeing or coating may alter the color.