The mineral was called Praesodynimium, a polysyllabic mouthful which meant simply that it was an unstable crystalline isotope of sodium that broke down eventually into ordinary sodium (hence "prae-":before; "sod-":sodium), which was possessed of extreme kinetic potentials ("dyn-":power), and was first extracted from sodium compounds by a Canadian scientist ("-imium" instead of the more American "-inum" or even "-um"). This crystal had the happy habit of electrical allergy. When subjected to even a mild electric current, it avoided the consequent shakeup of its electronic juxtaposition by simply vanishing from normal space until the power was turned off. The nice part about its disappearance--from an astronaut's point of view--was that the crystal took not only itself, but objects within a certain radius along with it. It turned out that a crystal of Praesodynimium the moderate size of a sixteen-inch softball would warp a ninety-foot spaceship into hyperspace without even breathing hard. Of course, it would warp anything _else_ within a fifty-foot radius, too; so it was only turned on after the ship had ascended beyond planetary atmosphere, lest a large scoop of landing-field, not to mention a few members of the ground crew, be carried away with the ship. In her eagerness to investigate the now-attainable stars, Earth had soon exhausted her sources of the mineral. Worse, the crystal, being unstable, had a half-life of only twenty-five years. That meant that a ship using it had a full-range radial margin of about five years before the crystal ceased warping the ship-inclusive area. Until some way was discovered to get into hyperspace without using Praesodynimium--and its actual function was as much a mystery to scientists as an automobile's cause-and-effect is to a lot of drivers; very few people can describe the esoteric relationships between the turning of the ignition key and the turning of the rear wheels--the mineral was worth ten times its weight in uranium 235. Sirius II had been found to be as rife with the mineral as a candy store is with calories. Hence the colony. For so long as the ore held out the planet would be regarded with fond respect and esteem by any and all persons who had investments, relatives or even just interest in the Space Age and its contingent programs. * * * * * So it was with considerable trepidation that Earth received the news that the mines on Sirius were no longer being worked. Oh, yes, there was still ore--enough to keep the planet profitable for another century. The trouble was the miners. They weren't coming out of the mines anymore. And no one who went inside to look for them was ever seen again, either. Naturally, mining slacked off. The men refused to set foot in the mines until somebody found out what had happened to their predecessors.