Oxygen in Rocks: A Basis for Petrographic Calculations

Abstract

The standard cell is defined as a rock unit containing 160 oxygens. The sum of the cations (silicon and metals) associated with this unit is very nearly 100 in all ordinary rock types. It is shown that, by using the standard cell as a basis, important petrogenetic relations can be surveyed and quantitatively defined more satisfactorily than by using any other method of petrographic calculation, including the norm method.