RE: I'll tell 'ya WHY not.LOL. I just inboxed Samosa about that.
The magnesium rock with platinum and chrome byproduct (the other way around actually) is the only way to go.
For fun, carbonizing Dunite is a CO2 capture technology that ends up with magnesian dolomite or magnesite, as a product, depending on the process.
2Mg3Si2O5(OH)4+ 3CO2 ? Mg3Si4O10(OH)2+ 3MgCO3 + H2O