Within 10 kilometers of sleepy Meldrum Bay, Ontario, where tourists’ tents dot the lawn between the general store and the marina, Canada’s largest marine quarry crushes, sorts and ships 5 million metric tons of dolomite rock annually. Around the point from the clapboard 19^th century lighthouse guarding Mississagi Straight, computer-driven 100-foot high conveyors feed blended ore into the holds of Great Lakes freighters. And within hailing distance of pleasure boats trolling for chinook salmon, huge ships laden with 20,000 tonnes of Lafarge product make for Lake Huron and the locks at Saulte Sainte Marie and the Welland Canal.