The notion of "distinguishibility" between bulk elastic parameters on the basis of the Gibbs energy deformation energy.

The present work aims in discussing a principle that distinguishes between elastic parameters sets ( Ko, K', Vo,...), on the basis of an energetic criterion: once a reference set is given, another one can be fixed (minimum), so that they are as close as possible to each other, but yield non-equivalent deformation energy curves, deltaGdeform. Delta G deform calculated using the equation of state (EoS), and its uncertainty, sigma [delta Gdeform], obtained by a propagation of the errors affecting parameters set are crucial to fix which mineral assemblage forms at P-T conditions and allow one to assess the reliability of such a prediction. We explore some properties related to the principle introduced, using the average values of the elastic parameters found in literature and related uncertainties for di-octahedral mica, olivine, garnet and clinopyroxene. Two elementary applications are briefly discussed: the effect of refining V0 in fitting EoSs to P-V experimental data, in the case of garnet and omphacite, and the phengite 3T-2M1 relative stability, controlled by pressure.