The new mineral coutinhoite, ideally Th x Ba(1−2x) (H 2 O) y (UO 2) 2 Si 5 O 13 · H 2 O, with 0 ≤ x ≤ 0.5 and 0 ≤ y ≤ (2 + x), occurs as a secondary hydrothermal mineral in the Córrego do Urucum granitic pegmatite, Lavra Urucum, Galiléia Co., Minas Gerais, Brazil.Coutinhoite is intimately associated with weeksite, phosphuranylite, meta …