When sourcing Neodymium (Nd), the most critical factor is purity levels, typically ranging from 99% to 99.99% (TREM - Total Rare Earth Metals). Buyers must distinguish between Neodymium Metal and Praseodymium-Neodymium (PrNd) Oxide/Metal, as the latter is more common for magnet production. Ensure the supplier provides a Certificate of Analysis (COA) detailing the specific impurities like Iron (Fe), Silicon (Si), and Calcium (Ca), which can significantly affect the magnetic properties of the final product.