 Val and Ron's geiger is programmed to identify:
THE HUNTED HEROES By ROBERT SILVERBERG The planet itself was tough enough—barren, desolate, forbidding; enough to stop the most adventurous and dedicated. But they had to run head-on against a mad genius who had a motto: Death to all Terrans! I reached over and turned up the pressure on her oxymask to make things a little easier for her. Val's usually about the best wife a guy could ask for, but when she wants to be she can be a real flying bother. Nothing but what had stopped us could stop a sandcat: sand in the delicate mechanism of the atomic engine. "Maybe there isn't any uranium in this sector at all. When Val's tired and overwrought there's no sense in arguing with her. We had wandered fruitlessly over the red sands all day, both of us listening for the clicks of the counter. And the geigers had been obstinately hushed all day, except for their constant undercurrent of meaningless noises. Even though the Martian gravity was only a fraction of Earth's, I was starting to tire, and I knew it must have been really rough on Val with her lovely but unrugged legs. She had been just as much inflamed by the idea of coming to Mars to help in the search for uranium as I was. We knew the pay was poor, but we had felt it a sort of obligation, something we could do as individuals to keep the industries of radioactives-starved Earth going. And we'd always had a roving foot, both of us. No, we had decided together to come to Mars—the way we decided together on everything. I didn't dare turn up her oxy pressure any higher, but it was obvious she couldn't keep going. 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. "What'samatter, Ron?" I watched her, sleeping peacefully, a wayward lock of her soft blonde hair trailing down over one eyebrow, and it seemed hard to believe that we'd exchanged Earth and all it held for us for the raw, untamed struggle that was Mars. It's because we wanted to keep what we had. The Geig Corps preferred married couples, working in teams. We had no ties on Earth that couldn't be broken without much difficulty. The wind blasted a mass of sand into my face, and I felt it tinkle against the oxymask.
 Uranium
 The Sandcat  The Dome  Uranium  humans