Working on a data set with bio markers. This is a classification problem and I'm having some troubles finding any information concerning the process of growing the trees in the R package "randomForest". Does any one familiar with the learning method know what the standard impurity measurement is when growing the full trees in R for a classification problem? The gini index seems to be used for a quick look at the variable importance, does that imply it is used as standard when actually growing the trees?