The Chemical Variability of some Common Igneous Rocks

The chemical variability of 39 groups of igneous rocks has been investigated using a data base of 26,373 published analyses. Each group was extracted from the data base using the name given in the reference from which the analysis was collected. The numerical data for each group includes wt. per cent and molecular per cent means, standard deviations, C.I.P.W. norms, Niggli values, the first three eigenvalues and eigenvectors together with a breakdown of the geographical distribution of the analyses used. Nine variation diagrams are also given for each group.