mineral
Polished banded agate
Banded chalcedony, microcrystalline quartz (SiO₂)
AI-generated identification · may be incorrectMohs hardness 6.5–7; brown, gray, and cream parallel bands with a glossy polish. Quartz has a trigonal crystal structure, but its microscopic crystals are not visible; cleavage is absent and fracture is typically conchoidal.
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Physical properties
Mohs hardness 6.5–7; brown, gray, and cream parallel bands with a glossy polish. Quartz has a trigonal crystal structure, but its microscopic crystals are not visible; cleavage is absent and fracture is typically conchoidal.
Formation & geological history
Silica-rich fluids deposited successive chalcedony layers in a cavity, commonly in volcanic rock. Agates formed in many geological periods; this specimen’s age and locality cannot be determined from the image.
Uses & applications
Used for jewelry, ornaments, and lapidary collecting; agate is also used in some precision components and decorative stonework.
Geological facts
Agate is a variety of chalcedony, not a separate mineral species; its distinctive bands record changes in conditions during silica deposition.
Field identification & locations
Look for translucent, curved or parallel bands and a waxy-to-glassy luster; common sources include Brazil, Uruguay, India, and the United States. The polished surface limits field identification of its host rock.
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