Rick wasn't. "But what is it?" he asked.
"The most valuable kind of ground in the world," Riddle said. "So far as anyone knew up to now, such pipes have occurred only in Africa. The one I saw was at Kimberley. The name came from there. This is kimberlite."
Rick knew of only one kind of valuable that was associated with Kimberley, and the thought was so staggering that he was almost afraid to say it out loud. "You mean that this is the stuff diamonds are found in?"
"Exactly," Riddle said.
Rick fished the handful of crystals from his pocket and stared at them unbelievingly. "Then these," he said hoarsely, "must be diamonds!"