The second part of the work - the surfaces of the stone, their inner polished sides are reflected in each other, the outer as if they bend under the gesture of a cord giving the appearance of softness, sand softly forming, stone particles yielding to foot pressure. Footprints in the sand...
Internal surfaces polished, hard, "granite" are reflected in each other, external - soft, give up, bending the gesture of threaded string, sand - a promise of stone breakup.