[en] The uranium deposit at Campo do Cercado is the first one in Brazil to reach the stage of mining operations. Located in the alkaline volcanic complex of Pocos de Caldas, the deposit is divided into three ore bodies which lie at the edge of a secondary crater in the caldera. Uranium ore occurs in the primary form in association with volcanic breccia belts (body A), as well as a result of hydrothermal action (body B); it is also present in the secondary form (body E) as a product of the leaching of the breccia belts by the oxidation front, followed by concentration and deposition in a reduction zone. The mineralization takes the form of black uranium oxides (UO₂/UO₃), and, more rarely, coffinite. Pyrite, galena and fluorite are almost always present. Molybdenum is also found in close association with the uranium ore in quantities considered economically viable. The ore reserves of the Pocos de Caldas plateau are estimated at 26,800 t. (author)