mineral
Tumbled blue-gray agate
Microcrystalline quartz (SiO₂), commonly chalcedony; exact identification is uncertain from the photo
AI-generated identification · may be incorrectPolished, opaque-to-translucent blue-gray pebble with a pale curved band. Quartz hardness is about 7 Mohs; vitreous to waxy luster, trigonal crystal structure at the microscopic level, and no cleavage; specific gravity is about 2.6.
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Physical properties
Polished, opaque-to-translucent blue-gray pebble with a pale curved band. Quartz hardness is about 7 Mohs; vitreous to waxy luster, trigonal crystal structure at the microscopic level, and no cleavage; specific gravity is about 2.6.
Formation & geological history
Agate forms as silica-rich fluids fill cavities in volcanic rocks, depositing chalcedony in layers. It may be millions of years old; the specimen appears tumbled and polished after formation.
Uses & applications
Used for jewelry, beads, ornaments, and lapidary collections; agate is also used in small decorative and precision objects.
Geological facts
Agate banding records successive changes in silica deposition and fluid chemistry.
Field identification & locations
Look for curved or concentric bands and a waxy appearance; common sources include Brazil, Uruguay, India, and the United States. The visible banding is consistent with agate, though a photograph cannot confirm it.
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