To further expand on this
I've now quantified Smithsonian dolomite using a calcite and MgO standard and C by difference - because carbon coated
Result as follows
Sum 1
C 0.0968
O 0.5498
Mg 0.1339
Ca 0.2195
So too much Oxygen and not enough C, I'd like to try oxygen by stoichiometry and carbon by difference but only choice of one or other
Thanks