Hi.,

(The molecular weight for each is calculated from their atomic weights.) 2) Multiply the molecular proportion for each oxide by the # of oxygen atoms present in each oxide. This gives the O atomic proportion.

1) Divide each oxide constituent by the formula weight of the oxide. This gives you the Molar Proportions of each oxide. 2) Multiply the molar proportions of each oxide by the number of cations in the oxide. This gives you the molar proportions of cations in your mineral.

The basic steps for formula calculation are:

Atoms per formula units (apfu): numbers of atoms in a chemical formula. O-Factor: the apfu' value scaled to a standard chosen number of oxygens. based on the simplified mineral formula for a given mineral species.

The question is about sulphides and they do not contain oxygen, I firmly believe. For sulfides, the conversion is very easy. The condition is that we know what mineral it is. It is based on the atomic percent (not weight percent) of the pure elements and this composition is only normalized to the required number of sulfur atoms in the formula or to the number of cations.

Yes. it can be done by calculating the atomic proportion by dividing the wt% by the atomic weight of each element and calculating the subscripts for the empirical formula. You can see this link for more details.

https://courses.missouristate.edu/emantei/mineralogy/miner-chem-calc.html