question:  Why does Evans have difficulty identifying crystals?
context: The meteor, a pebble, a little larger than a match head, traveled through space and time since it came into being. The light from the star that died when the meteor was created fell on Earth before the first lungfish ventured from the sea. 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. The chromite petered out in a month and a half, and he was lucky to break even. But his oxygen was too carefully measured; there was a four-day reserve. 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. This was to allow the air-conditioning system to function properly, and to prevent air loss in case of the highly improbable meteor damage. 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."
output:  They were not actually crystals to begin with
options:  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