Pyrrhotite
Fe 0.8%, S 1%,

estimated elemental composition and molecular weight 
Minerals with the same name may vary widely in appearance and composition, and very few are >99% (reagent grade) pure.

Gram formula weight (molecular mass) = 76.742


Minerals may vary in elemental composition and impurity levels. The mineral also contains nickel.
Wikipedia Page:

Pyrrhotite
is defined with respect to the entities below:
The entities below are defined with respect to:
Pyrrhotite
Mineral (generic)


chemical compound molecule metal molecular science reaction mechanism ionic material acid base geometry reactivity synthesis science knowledge chemistry Lewis