In Rust, programs are often written using iterators, but these pose problems for verification: they are non-deterministic, infinite, and often higher-order, effectful and built using combinators. We present a general framework for specifying and reasoning with Rust iterators in first-order logic. Our approach is capable of addressing the challenges set out above, which we demonstrate by verifying real Rust iterators, including a higher-order, effectful Map. Using the Creusot verification platform, we evaluate our framework on clients of iterators, showing it leads to efficient verification of complex functional properties.