mineral
Polished banded agate heart
Microcrystalline quartz (SiO₂), primarily chalcedony with iron-oxide inclusions
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; gray, mauve, and brown concentric/flow bands; vitreous to waxy luster; cryptocrystalline structure with no visible cleavage and conchoidal fracture. The smooth heart shape is human-cut and polished.
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Physical properties
Hardness 6.5–7 Mohs; gray, mauve, and brown concentric/flow bands; vitreous to waxy luster; cryptocrystalline structure with no visible cleavage and conchoidal fracture. The smooth heart shape is human-cut and polished.
Formation & geological history
Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing layers of chalcedony over time; coloration commonly comes from iron and manganese impurities. Individual layers may form over thousands to millions of years, often in Cenozoic or older volcanic terrains.
Uses & applications
Used for ornamental carvings, cabochons, paperweights, and lapidary collectibles; banded varieties are popular in jewelry and décor.
Geological facts
Agate is a variety of chalcedony rather than a separate mineral species. Its curved bands record changing chemistry and fluid conditions during cavity filling.
Field identification & locations
Identify it by translucent layered banding, very high polish, and hardness sufficient to resist scratching by steel. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the United States.
