"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 ...
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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.[page needed]" - (en.wikipedia.org 09.07.2022)