Space-Wolf by Ray Cummings - The lure of precious zolonite drew Morgan to barren Titan—to find a weird beast-empire ruled by a cold-eyed Earth-girl queen.

Solo Morgan laid his small portable spectroscope on the rock and sat down beside it to rest. He was panting, breathless from the climb up to these precipitous heights, even though the gravity here on Titan was less than that of Earth. It was night. The pallid little Sun had swiftly set behind a distant line of jagged mountain peaks. At the other horizon Saturn was rising, a monstrous glowing ball with a foreshortened segment of the rings spreading in a great iridescent flame of pale prismatic color across half the sky.

From here, Solo Morgan could just see the tiny blob of his one-man space-ship where he had left it down in the hollow. "He travels fastest who travels alone," had always been Solo Morgan's motto. But now at the age of twenty-eight, a big, rangy, handsome fellow with curly, crisp brown hair, it seemed to Morgan that he was somewhat a failure. So far he had failed to strike it rich; and a single big strike had always been what he was after. He set his jaw grimly as he thought of it. Well, now was the time. There was a lode of Zolonite here on this moon of Saturn. The spectroscopic evidence of it had been faint, yet unmistakable. Doubtless it was a single, small concentration; Zolonite perhaps in an almost pure state. Immensely more valuable than radium; more valuable, than any other radioactive substance known to earth.

Morgan stood up, rested, to continue his climb. By all that he had been able to determine from the faint spectroscopic bands, and the intensity registers which he had so carefully used in that circling flight around the bleak, uninhabited satellite, the Zolonite deposit must be somewhere in this neighborhood.