The coefficient of friction can vary depending on several factors such as the specific surface finish, presence of any coatings or sealants, and the angle of inclination. Without specific information about the surface condition of the Filled Norways Rhomben Porphyry tiles, it is not possible to provide an accurate value for the coefficient of friction. It is recommended to refer to the manufacturers specifications or contact the supplier for detailed information on the coefficient of friction for this particular tile.