Polyhedral Agate from Paraíba, Brazil
Polyhedral Agate is a rare, naturally angular variety of agate from Garguelo Farm near Cachoeira dos Índios in Paraíba, Brazil. Its flat-sided nodules contain layered chalcedony, sometimes surrounding incompletely filled central cavities. Although several explanations have been proposed for its unusual geometry, the exact formation process remains unresolved.