Abstract: A method and apparatus for determining the composition of glass, and for sorting glass according to composition. Glass of unknown composition is irradiated and an x-ray fluorescence spectrum is detected from the glass. The detected x-ray fluorescence spectrum is then compared with a plurality of fluorescence spectra corresponding to glasses of known composition. The glass of unknown composition is then determined to correspond in composition to the glass of known composition having an x-ray fluorescence spectrum most closely matching the spectrum detected from the glass of unknown composition. The glass may then be sorted according to determined composition. In operation, a substantially continuous stream of glass pieces is irradiated and detected while the stream is moving. Once the composition of a piece of glass in the stream is determined, it is diverted into an appropriate container of like compositioned glass.