  VO$_2$ is a unique phase change material with strongly anisotropic electronic
properties. Recently, samples have been prepared that present a co-existence of
phases and thus form metal-insulator junctions of the same chemical compound.
Using first principles calculations, the optical properties of metallic and
semiconducting VO$_2$ are here discussed to design self-contained natural
optical metamaterials, avoiding coupling with other dielectric media. The
analysis of the optical properties complements the experiments in the
description of the vast change in reflectance and metallicity for both
disordered and planar compounds. The present results also predict the
possibility to realize ordered VO$_2$ junctions operating as efficient
hyperbolic metamaterials in the THz-visible range, by simply adjusting the
ratio between metallic and insulating VO$_2$ content. The possibility to excite
propagating {\em volume plasmom polariton} across the metamaterial is finally
discussed.
