Instead of being produced constantly (.06 per second with my current bonuses) Neodymium will not be made at all for several minutes, and then suddenly those several minutes worth of production will happen all at once.
Have a look at the multi ore entry in the Factoriopedia. Neodymium has a very low probability to be produced, but when it does get produced, 1000 neodymium items are given at once.
