A non-destructive method to determine the percent composition and relative purity of bulk solid phase mixed fullerene samples using Raman spectroscopy is described. This ratiometric method has a significant advantage in ease of use over other methods, in that the samples are analyzed in a short time, as solids in suspension, with minimal sample pre-preparation, using easy to operate instrumentation. The ratio of unique vibrational bands vs. percent composition is used to construct a calibration curve, and a detection limit estimated in the presence of chemical noise.