 Val and Ron's geiger is programmed to identify:
The planet itself was tough enough—barren, desolate, forbidding; enough to stop the most adventurous and dedicated. Nothing but what had stopped us could stop a sandcat: sand in the delicate mechanism of the atomic engine. And the geigers had been obstinately hushed all day, except for their constant undercurrent of meaningless noises. The geiger kept up a fairly steady click-pattern, but never broke into that sudden explosive tumult that meant we had found pay-dirt. I stopped, slipped out of the geiger harness, and lowered myself ponderously to the ground. He wore an outmoded, bulky spacesuit and a fishbowl helmet, all but the face area opaque. The oxygen cannisters weren't attached to his back as expected, though. He was holding in his left hand the tanglegun with which he had entrapped us, and a very efficient-looking blaster was in his right. He reached for the tanglegun, flipped the little switch on its side to MELT, and shot a stream of watery fluid over our legs, keeping the blaster trained on us all the while. Val and I helped each other to our feet as best we could, considering our arms were still tightly bound against the sides of our oxysuits. Earth needed radioactives, and the only way to get them was to get out and look. The great atomic wars of the late 20th Century had used up much of the supply, but the amount used to blow up half the great cities of the world hardly compared with the amount we needed to put them back together again. And that started the chain of events that led Val and me to end up as a madman's prisoners, on Mars. With every source of uranium mined dry on Earth, we had tried other possibilities. Project Sea-Dredge was trying to get uranium from the oceans. In a decade or so, our power would be just about gone. It's a stopgap effort, just to keep things moving until Project Sea-Dredge starts functioning. Enter the Geig Corps: volunteers out on the face of Mars, combing for its uranium deposits. For a puzzled moment I thought it was our Dome, the settlement where all of UranCo's Geig Corps were located, but another look told me that this was actually quite near us and fairly small. He herded us off to one side of the airlock, uttered a few words keyed to his voice, and motioned us inside when the door slid up. When we were inside he reached up, clumsily holding the blaster, and unscrewed the ancient spacesuit fishbowl.
 Uranium
 The Sandcat  The Dome  Uranium  humans