Every curling stone in serious competition is cut from rock taken out of two places on earth: an uninhabited Scottish island that is also a protected bird colony, and a quarry on the coast of North Wales. Canada has more than 800 affiliated curling clubs and a record 158,199 registered curlers. Nobody publishes how much granite that adds up to, so we worked it out.
The rule that creates the demand is short and rarely quoted. Section 4 of Curling Canada’s rules for general play says that two sets of eight stones shall be provided for each sheet of play. Sixteen stones, per sheet, every sheet, before a single game is played. The same section caps a stone at 44 pounds (19.96 kilograms) including handle and bolt, sets a floor of 38.5 pounds (17.46 kilograms), and limits it to a circumference of 36 inches with a minimum height of 4.5 inches.
