Pyrrhotites: Stoichiometric Compounds with Composition Fe n -1 S n ( n ≥ 8)

Abstract

A new type of natural pyrrhotite, orthorhombic 11C type (a = 6.892, b = 11.952, c = 5.744 x 11 angstroms), and the hexagonal 6C type (a = 6.89, c = 5.76 x 6 angstroms) are described. Their compositions are Fe₁₀S₁₁ and Fe₁₁S₁₂, respectively. Pyrrhotites stable in nature have essentially stoichiometric composition, Fe_n-_lS_n (n≥8), with the structures of n/2C type for n even and of nC type for n odd. The solid solutions between Fe₁₁S₁₂ and Fe₁₀S₁₁, and between Fe₁₀S₁₁ and Fe₉S₁₀ are considered metastable in nature.