A method and apparatus enables testing of sifting segregation of a particulate solid mixture in a storage bin or hopper. The apparatus makes use of a convergently and divergently angled hopper for collecting the mixture. The apparatus further makes use of a minimally-shearing feeder mechanism supplying a desired flow of mixture, with minimal to no sifting segregation, to the angled hopper. A collection mechanism removes samples of the mixture from the angled hopper for analysis with minimal disruption of the particles of the mixture relative to each other. Thus, samples resulting from the testing apparatus, and corresponding method, are highly representative of mixture conditions within a larger storage hopper.