mineral

Polished banded agate sphere

Agate, microcrystalline quartz (SiO₂), a chalcedony variety

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent gray-brown with dark curved bands and a vitreous to waxy luster. Trigonal quartz in microscopic crystals; no visible cleavage, conchoidal fracture. The black lines may be natural inclusions or added decorative treatment.

Identified October 16, 2026More mineral →

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Physical properties

Formation & geological history

Agate forms as silica-rich fluids fill cavities and deposit successive chalcedony layers, commonly in volcanic rocks. Its age depends on the host rock and cannot be determined from the photo.

Uses & applications

Polished spheres are used for display and collecting; agate is also used in jewelry and ornamental objects.

Geological facts

Agate banding records changing conditions during silica deposition; polished spheres can reveal patterns hidden in rough material.

Field identification & locations

The curved, irregular bands and translucent chalcedony appearance are consistent with agate, but the photo cannot confirm whether the dark bands are natural. Agates occur worldwide, notably in Brazil, Uruguay, India, and the United States.