High-pressure behaviour of benitoite

From a crystallographic point of view, is rather interesting being the prototype structure for the P6 ̅2c space group and it has been the focus of previous high-pressure crystallographic investigations due to the presence of the (Si3O9)6– silicate-ring units (Hejny et al. 2012). Indeed, numerous synthetic germanate compounds are either isostructural to benitoite or represent a topologically equivalent structure of reported lower (in all cases trigonal) symmetry. For these reasons the high-pressure behaviour of benitoite will be studied up to 20 GPa in a DAC using He as P-transmitting medium.