  Crystal quartz is a well-known anisotropic medium with optically active
phonons in the THz region where hyperbolic phonon-polaritons can be excited.
Here, we use this material to illustrate how the behavior of bulk and surface
hyperbolic polaritons can be drastically modified by changing the orientation
of the crystal's anisotropy axis with respect to its surface. We demonstrate,
both theoretically and experimentally, phenomena associated with the
orientation of hyperbolic media. We show the consequences of slight changes in
the crystal's orientation in various ways, from the creation of hyperbolic
surface phonon-polaritons to the demonstration of oriented asymmetric
transmission of radiation passing through a hyperbolic medium.
