The second sentence in the statement "In terms of its atomic structure, each Fe center is linked to three As atoms and three S atoms. The material can be described as Fe3+ with the diatomic trianion AsS3−." may be somewhat misleading, implying the presence of ferric iron in a mineral otherwise stable in reducing regimes. Schaufuss et al. (American Mineralogist 85:1754–1766, 2000), although in agreement with the Fe, Ar, and S coordination mentioned here, describe the arsenopyrite dianion as (As-S)^(2-), thus making the iron ferrous by balance.