The Formfjord 'Ruhrsteine' pebble is a packaged concrete pebble made for the ultimate stone-skipping enthusiast. Designers Fabian Baumann and Sönke Hoof were influenced by the German language, which has 1,000 words for "skipping rocks." Cast from real stone, the pebbles are collected from the side of the Rhur river.
Each Formfjord 'Ruhrsteine' pebble is encrusted with a "throw-away-symbol" that claims to make the tosser happy once the stone is flung--its only practical use. I wonder if the Berlin-based design team ever re-collects one of their manmade stones while searching for new material.