Allot Minor Elements to Accessory Minerals. Later on, Ti may need to be alloted to perovskite or rutile. Allot Calcium and Aluminum to anorthite. If there is no silica deficit, calculation is complete. Calculating the Norm Preliminary Comments Convert all weight percentages to molecular percentages .
Formulas follow common computer program syntax.
Any provisional amounts remaining at the end become final amounts. From here on, all FeO and MgO go to pyroxene plus olivine, but their relative proportions are maintained in all minerals. The sum of MgO plus FeO is designated FM in what follows. Add these amounts to the previously-formed minerals. Add these amounts to the previously-formed minerals.