Insurgence - S2-E12
Revealing mistake: After Lex's employee walks out of the office, Lex gets mad and throws most of the objects off his desk. Prior to this, we see a computer screen displaying something. When the objects go flying off and hit the wall, we see that it wasn't actually a computer screen but a prop that was made look like one. It was just the frame, a piece of paper that served as the display covered by clear plastic to make it look like an actual computer screen.
Insurgence - S2-E12
Continuity mistake: When Lex speaks with the Lieutenant, watch Clark and Jonathan in the background. They are seen standing by a News Now van and looking up at the Daily Planet. When the camera cuts to them, they are shown walking past the News Now van again.
Insurgence - S2-E12
Continuity mistake: When Lana is meeting with the Small's over coffee at the Talon and Mr. Small gets more coffee for himself and is wife, he picks up his cup and his wife's. Then when he comes back he puts down the coffee for himself and Lana.
Answer: The kryptonite only creates mutations when it reacts with the environment and an individual. Remember, the FDA and several environmental groups did check out Smallville after the meteor shower, but found no danger in the rocks. Obviously they're not always emitting mutating rays, or all the flora and fauna of the surrounding area would be horribly mutated.
Phoenix