National Geographic : 1968 Jul
Telltale chatter of Geiger counters pinpoints a narrow vein of uranium ore 2,200 feet underground at Eldorado, Saskatchewan. To guide miners, these geologists will spray the vein with paint. EKTACHROME(RIGHT)AND KODACHROME © N.G.S. Powdery uranium oxide, called yellow cake, clings to a filter press at the plant of Eldorado Mining and Refining Ltd. A ton of ore precipitates into three and a half pounds of the concentrate, not harmfully radioactive at this stage. The yellow cake goes to a refinery in Ontario or abroad for further processing into fuel for nuclear reactors. In the 1950's Canadian uranium mines supplied military stockpiles; a second boom, now in progress, provides atomic fuel for peaceful uses.