In 1939, just before the start of World War II, Albert Einstein wrote a letter to President Franklin D. Roosevelt with a muted warning: “The element uranium may be turned into a new and important source of energy in the immediate future … It is conceivable … that extremely powerful bombs of this type may thus be constructed.” Einstein’s letter mentioned four known uranium sources: the United States, which “has only very poor ores of uranium in moderate quantities”; Canada and the former Czechoslovakia, where “there is some good ore”; and Congo—“the most important source of uranium.” According to Jean Bele, a Congolese nuclear physicist at MIT, 100 kilograms of Congolese uranium ore could yield about 1 kilogram of refined uranium. The same amount of ore from the other locations would yield only 2 or 3 grams of the refined uranium necessary for such a weapon.
The mining company typically built fenced-in compounds that resembled prison camps for the workers and their families; the company initially gave each family about 43 square feet—the size of a small garage—and weekly food rations. At work, miners sorted uranium ore by hand. One person described a piece of Shinkolobwe uranium as a block “as big as a pig.” It was “black and gold and looked as if it were covered with a green scum or moss.” He called them “flamboyant stones.”
The director of Union-Minière du Haut-Katanga was Edgar Sengier, a pale Belgian man with a sharply cut mustache. Having seen Germany invade Belgium in World War I, Sengier was unsure about what Hitler’s invasion of Poland in September 1939 foretold. Would Belgium—or even the African colonies—be next? So in October, he fled Belgium for New York City and transferred the mining company’s business operations there. However, before he had set up shop, a British chemist and the Nobel Prize–winning scientist Frédéric Joliot-Curie, son-in-law of Marie Curie, tipped off Sengier that the uranium in Congo might become essential in the war. The next fall, Sengier ordered that it be shipped to New York.
So Congolese workers carried and loaded the ore. It was sent by train to Port Francqui (now Ilebo), then by boat down the Kasai and Congo Rivers to the capital, Leopoldville (now Kinshasa). At the port of Matadi, the uranium began its trek across the Atlantic Ocean, past German U-boats, to a warehouse on Staten Island. Sengier stored more than 2.6 million pounds of ore in the States. About 6.6 million pounds remained in Shinkolobwe.
