Pyrrhotite is an iron sulfide mineral with the formula Fe₍₁₋ₓ₎S (x = 0 to 0.2).
 It is a nonstoichiometric variant of FeS, the mineral known as troilite.

Pyrrhotite is also called magnetic pyrite, because the color is similar to pyrite and it is weakly magnetic.
The magnetism decreases as the iron content increases, and troilite is non-magnetic.
Pyrrhotite is an iron sulfide mineral with the formula Fe₍₁₋ₓ₎S (x = 0 to 0.2).  It is a nonstoichiometric variant of FeS, the mineral known as troilite.
Pyrrhotite is also called magnetic pyrite, because the color is similar to pyrite and it is weakly magnetic. The magnetism decreases as the iron content increases, and troilite is non-magnetic.
Pyrrhotite