We study codimension 1
quasiminimizing surfaces in ℝn, and establish uniform rectifiability and other
geometric properties of these surfaces. For instance, their complementary
components must be John domains. In fact we give a complete characterization of
quasiminimizers. As an application we show that sets which are not too large and
which separate points in a definite way must have a large uniformly rectifiable piece.
In this way we use area quasiminimizers to solve a problem in geometric measure
theory.