Abstract
The practicability of estimating chemical variation in a rock from the mode is investigated. Using the modal percentages, determined with a Dollar integrating micrometer, and standard chemical compositions of minerals, the molecular proportions were calculated and von Wolff values determined and plotted. It was found that a good idea of the chemical variation could be obtained and that the accuracy of the modes and derived chemical analyses is consistent within a suite of rocks. The method was used in examining the contact relations of a granite and quartzite in northwest Donegal, Ireland, and the variability of the granite.
GeoRef, Copyright 2004, American Geological Institute. Reference includes data from Bibliography and Index of Geology Exclusive of North America, Geological Society of America, Boulder, CO, United States