mineral
Polished banded agate
Agate, a microcrystalline variety of quartz (SiO₂), often chalcedony
AI-generated identification · may be incorrectMohs hardness 6.5–7; glossy, waxy luster with gray, mauve, and brown bands. Trigonal quartz in microscopic fibers; no distinct cleavage, conchoidal fracture; specific gravity about 2.6.
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Physical properties
Mohs hardness 6.5–7; glossy, waxy luster with gray, mauve, and brown bands. Trigonal quartz in microscopic fibers; no distinct cleavage, conchoidal fracture; specific gravity about 2.6.
Formation & geological history
Silica-rich groundwater deposited successive layers in cavities, commonly in volcanic rocks. Agate formed in many geological periods; this specimen’s exact age and locality cannot be determined from the image.
Uses & applications
Used for jewelry, ornaments, cabochons, and collectible polished stones; agate is also used for small precision components.
Geological facts
Agate’s fine-scale color bands record changing conditions during silica deposition; many specimens are polished to reveal these patterns.
Field identification & locations
The rounded, polished shape and curved internal bands identify it as agate, though the specific agate variety is uncertain. Agates occur worldwide, especially in volcanic regions; inspect banding and translucency, and use a hardness test only with permission.
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