Impurity separation characteristics of graphite were investigated along with its expansion. Inclusion states of typical clay minerals as impurity in the expanded graphite particles were observed and classified into four distinct types (Type I-IV). Removal of the minerals by the application of simple mechanical impact with Ro-Tap and scrubbing was performed with two expanded graphite specimens prepared from graphite concentrates of 93% fixed carbons from two different mines. It was found that the mechanical treatments were able to easily raise the carbon content to over 99.9%, depending on the impurity inclusion type.