There appears to be some confusion in the literature concerning the state of a granular mixture at the end of an ideal mixing process, and this may have influenced the basis on which some mixing indices were formulated. As an attempt to provide clarification, we quantitatively established the three characteristic states of a granular mixture - the completely unmixed, the perfectly ordered, and the randomly mixed states - by considering the relevant probability distributions. We demonstrated how one may derive the expected values of various mixing indices based on these probability distributions, and verified the results with a simple mixing simulation. Asymptotic arguments showed the randomly mixed state, not the perfectly ordered state, best describes a well-mixed granular mixture, while the two states become increasingly indistinguishable as the number of particles per sample increases. We revealed that unlike the Lacey index, which is normalised based on the randomly mixed state, the normalisation of the total entropy of mixing uses the perfectly ordered state, making it less than unity at the end of an ideal mixing operation - this has not been sufficiently highlighted by the authors proposing such indices. We found it interesting to analyse the Gini coefficient, a widely accepted measure of income inequality in economics, in the context of granular mixing. While not advocating its use, we noted that similar to the other indices, its expected values for the characteristic states are dependent on the choice of the basis of normalisation. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.