The model of zonal anisotropy, built from the nest of structures
having their own anisotropy, is flexible enough to be used as a model for
almost any type of experimental anisotropy.
However, the flexibility of this model must not be misused. When
a specified direction is differentiated (e.g., the vertical direction 
, of
the previous example), this direction must correspond to a preferential
direction of the mineralization. The known geology should always be
used as a guide when fitting a mathematical model
to a natural
variability.