Click Select to display the Mineral Selector dialog box for up to five minerals for which GeoSyn calculates an average using either the Voight-Reuss-Hill or Hashin-Shtrikman formulas specified.

Type the percentage of pore volume this mineral occupies. Note that you can't proceed beyond this dialog box until the combined volume of the minerals you've selected equals 100%.

Select Voight-Reuss-Hill if the matrix is fairly homogenous for a straight arithmetic averaging formula, or select Hashin-Shtrikman if the matrix is more complex.