mineral

Polished agate nodule

Agate, a banded variety of microcrystalline quartz (SiO₂)

AI-generated identification · may be incorrect

Cream, tan, and brown concentric bands with a waxy-to-vitreous luster; quartz crystal structure, Mohs hardness 6.5–7, and no cleavage. The cut face reveals the banding.

Identified October 15, 2026More mineral →

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Physical properties

Cream, tan, and brown concentric bands with a waxy-to-vitreous luster; quartz crystal structure, Mohs hardness 6.5–7, and no cleavage. The cut face reveals the banding.

Formation & geological history

Agate forms as silica-rich fluids deposit chalcedony in cavities, commonly in volcanic rocks. Its age varies with the host rock and deposit; the pictured piece’s locality and age cannot be determined from the image.

Uses & applications

Used for jewelry, ornaments, carvings, and collections; agate is also used in precision components and traditional decorative objects.

Geological facts

Agate’s bands often record successive changes in silica-rich fluids as a cavity fills.

Field identification & locations

Identify it by its fine-grained quartz, hardness, and curved or concentric bands; common sources include Brazil, Uruguay, India, and the United States. The photo shows a small cut or polished nodule, but its precise variety is uncertain.