Reliable determination of niobium and tantalum in Nb–Ta ores is analytically challenging due to the refractory nature of the matrix and pronounced spectral and matrix effects in ICP?OES. In this study, two chemically distinct fusion procedures – an established phosphate fusion and an optimized lithium metaborate (LiBO2) fusion followed by dissolution in a dilute HF/HNO3 mixture – were systematically compared. A dataset of 69 natural Nb–Ta mineral concentrates and one industrial synthetic material analyzed over a ten-year period was used for the comparison. Method equivalence was assessed using Deming regression with a heteroscedastic error structure. Trueness was evaluated using the CRM X1808 certified reference material and an in-house reference material characterized by X-ray fluorescence (XRF). Both fusion methods provided analytically equivalent results for Nb2O5 and Ta2O5 across the entire concentration range. However, borate fusion allowed simultaneous determination of a broader range of elements, including Na2O, P2O5, and SiO2. Although both approaches can be used to quantify most analytes, their applicability is partly complementary: phosphate digestion does not allow reliable determination of sodium and phosphorus, and SiO2 determination may be limited at higher concentrations. In addition, while both fusion techniques are considerably more rapid and more robust than conventional acid digestion, borate fusion also allows slightly faster sample preparation. Overall, fusion-based approaches represent an efficient and reliable strategy for the comprehensive analysis of complex Nb–Ta matrices.