gemstone

Banded agate bangle

Agate (microcrystalline quartz, SiO₂), likely gray-blue chalcedony with parallel banding

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent gray, blue-gray, and white bands; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage; specific gravity about 2.60–2.65. The circular form is polished and shaped, so it is a processed geological specimen.

Identified September 5, 2026More gemstone →

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Physical properties

Formation & geological history

Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing successive layers of chalcedony over long periods, commonly during the Cenozoic or older volcanic episodes. Similar material is found in Brazil, Uruguay, India, Madagascar, China, Mexico, and the United States.

Uses & applications

Used for bangles, cabochons, beads, carvings, ornaments, and lapidary objects; its durability makes it suitable for everyday jewelry.

Geological facts

The fine bands result from repeated changes in silica chemistry, impurities, and fluid conditions during cavity filling. Blue-gray coloration may be natural or enhanced by treatment.

Field identification & locations

Identify by translucent concentric or parallel banding, waxy luster, high polish, and inability to scratch with a steel nail; glassy uniform material is a possible imitation. Inspect edges for dyed color concentration or fractures.