Kruger could not imagine why American geologists would want to go to the Virunga region of Zaire, in the northeast corner of the Congo rain forest. Zaire was the richest country in black Africa, in minerals-the world’s largest producer of cobalt and industrial diamonds, the seventh largest producer of copper. In addition there were major deposits of gold, tin, zinc, tungsten and uranium. But most of the minerals were found in Shaba and Kasai, not in Virunga.
Kruger knew better than to ask why the Americans wanted to go to Virunga, and in any case he had his answer soon enough. Once the expedition passed Lake Kivu and entered the rain forest, the geologists began scouring rivers and streambeds. Searching placer deposits meant that they were looking for gold, or diamonds. It turned out to be diamonds.
But not just any diamonds. The geologists were after what they called Type IIb diamonds. Each new sample was immediately submitted to an electrical test. The resulting conversations were beyond Kruger-talk of dielectric gaps, lattice ions, resistively. But he gathered that it was the electrical properties of the diamonds that mattered. Certainly the samples were useless as gemstones. Kruger had examined several, and they were all blue from impurities.
For ten days, the expedition had been tracing back placer deposits. This was standard procedure: if you found gold or diamonds in streambeds, you moved upstream toward the presumed erosive source of the minerals. The expedition had moved to higher ground along the western slopes of the Virgunga volcanic chain. It was all going routinely until one day around noon when the porters flatly refused to proceed further.