This work describes the methodology developed for testing the capability of a mathematical function to synthesize the composition distribution of comminuted polyphase materials. The standard Beta distribution, considered to meet the requirements for such modeling, was proposed and assumed as the body of a mixed model, which was tested. Procedures involved obtaining experimental data and using it to test the Null Hypothesis. Tests led to conclude that the Mixed Model passed in a Kolmogorov-Smirnov (K-S) test of adherence, at a level of 5%.