Latrappite is defined as a mineral with the perovskite structure with formula ABO 3 , in which A and B cation sites are in excess of 50 mol percent calcium and niobium, respectively. Type latrappite has 43.90 percent Nb 2 O 5 . It is orthorhombic, a=5.448, b=7.777, and c=5.553 A, sp. gr. is 4.40.