The coefficient of friction for Leathered Norways Black Wave Phyllite tiles can vary depending on the specific type of phyllite being used and the surface finish applied to it. Generally, phyllite is known to have a low to moderate coefficient of friction. To determine the exact coefficient of friction for Leathered Norways Black Wave Phyllite tiles, it is recommended to consult with the manufacturer or supplier of the tiles who can provide specific information on the products coefficient of friction.