  A hex sphere is a singular Euclidean sphere with four cones points whose cone
angles are (integer) multiples of 2*pi/3 but less than 2*pi. Given a hex sphere
M, we consider its Voronoi decomposition centered at the two cone points with
greatest cone angles. In this paper we use elementary Euclidean geometry to
describe the Voronoi regions of hex spheres and classify the Voronoi graphs of
hex spheres (up to graph isomorphism).
