The article mentions problems due to impurities a couple of times. If you grow an unsatisfactory crystal due to impurities, it will still be purer than the star

The article mentions problems due to impurities a couple of times. If you grow an unsatisfactory crystal due to impurities, it will still be purer than the starting material, so you could re-dissolve it to make a more pure solution for another attempt: https://en.wikipedia.org/wiki/Recrystallization_(chemistry) https://en.wikipedia.org/wiki/Recrystallization_(chemistry)