The 17 elements are not usually sold in their pure form , but instead are distributed in mixtures of varying purity , e.g. `` Neodymium metal ≥ 99 % '' .
The 17 elements are not usually sold in their pure form . They are usually distributed in mixtures of varying purity , e.g. `` Neodymium metal ≥ 99.5 % '' .