 Why does Evans have difficulty identifying crystals?
The shadow line between day and night could be seen from the Moon to be drifting across Australia. Evans, who had no watch, thought of the time as a quarter after Australia. Evans was a prospector, and like all prospectors, a sort of jackknife geologist, selenologist, rather. Once he followed a stampede to Yellow Crater, where he thought for a while that he had a fortune in chromium. This boiling lowered the temperature, and the condenser demonstrated its efficiency by quickly freezing the water in the tank. Evans sealed the turbine from the rest of the steam system by closing the shut-off valves. For example, because of an order of his stating that there would be no alcoholic beverages within the survey building, the entire survey was assured of a constant supply of home-made, but passably good liquor. Morning to him had no meaning at all, but he thought in the strictest sense that it would be morning on the Moon for another week. The solar furnace was a rough parabola of mirrors used to focus the sun's heat on anything that it was desirable to heat. Three of the nine banks of mirrors would not respond to the electric controls, and one bank moved so jerkily that it could not be focused, and it threatened to tear several of the mirrors loose. "Meteor shower," Cowalczk answered, "and that's not half of it. "That could hurt," Cowalczk admitted, "but there was only one of them." After the sun rose, Evans returned to the lava cave that he had been exploring when the meteor hit. These crystals," he said, "look a little like zeolites, but that can't be, zeolites need water to form, and there's no water on the Moon." One at a time, back in the tractor, he took the crystals out of the bags and analyzed them as well as he could without using a flame which would waste oxygen. One of the crystals that he thought was quartz turned out to be calcite, and one of the ones that he was sure could be nothing but calcite was actually potassium nitrate. All of these needed water to form, and their existence on the Moon puzzled him for a while. Then he opened the bag that had contained the unusual hexagonal crystals, and the puzzle resolved itself. What he had taken to be a type of rock was ice, frozen in a niche that had never been warmed by the sun. That's from here to Earth, of course.
 They were not actually crystals to begin with
 All of the crystals he found were very rare  He does not have much experience in doing so  They were not actually crystals to begin with  None of the crystals were native to the moon