Oco geodes are mined in northern Rio Grande do Sul province in Brazil. These geodes are quite popular given their smaller shape, thin skins, and wonderful agate in the shell with drusy quartz interiors. Many of these geodes also contain goethite crystals (or another related iron mineral). These geodes are approximately 138-127 million years old and are surface mined from outcrops in the Tres Pinheiros region of Rio Grande do Sul. Most Ocos are between 1-3 inches in diameter although some larger and smaller are also occasionally available. All of our Oco geodes are imported directly from the mine owner in Brazil. Information source - "Geodes, Nature's Treasures" by Cross/Zeitner (2006) and Geode Gallery's supplier in Brazil.
All of our opened Oco geodes are sold only as a pair, either individually or in a bulk flat, with each geode already cut and polished. We will not sell only one half of a matching pair. Please click on the desired specimen(s) below for more details. Please note that all pairs pictured below have some tissue paper wrapped around each half to protect the polished face/edge and for safe shipping - it is easily removable. For Oco geodes in their rough form (not cut open) and guaranteed hollow, please visit our Whole Oco Geodes - Brazil page.