Pyrrhotite 4C and dirty magnesiospinel standards

[Zack Gainsforth]

I'm looking for two standards: pyrrhotite 4C, and "dirty" magnesiospinel.

4C is pretty self-explanatory, but by "dirty" magnesiospinel, I mean a spinel with any of Fe, V, Cr, Mn, but at least 90% magnesiospinel.  Does anyone have such standards or at least have the minerals and have done EPMA on them? 

I'll FIB them and use them for TEM work, and it is helpful to have some idea of a homogeneity index even though once you get to the TEM scale, you can't count on EPMA homogeneity anymore.  I find that minerals from very equilibrated sources tend to work better this way.

Thanks,

Zack