Talk:Arsenopyrite

Latest comment: 9 years ago by Smokefoot in topic Untitled

Untitled edit

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. <ref>Schaufuss et al. (American Mineralogist 85:1754–1766, 2000)</ref>, 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. 134.102.70.246 (talk) 17:41, 13 May 2015 (UTC)Reply

Oxidation states are a great (or terrible) simplification, as is the classification that it is stable in "reducing regimes." These sulfides are semiconductors so localized models are imperfect. A classic WP:SECONDARY source is the book by Craig and Vaughan who indicate that marcasite is Fe(II) with long Fe---Fe distances (3.4A), arsenopyrite is related but Fe(III) but with alternating Fe-Fe bonds (2.9A) and non-bonds (3.5A) along one axis, and loellingite is Fe(IV) with all short Fe-Fe contacts (2.85 A) along the same axis. All are diamagnetic. Again, these are all very ionic descriptions, but within the ionic model, AsS2- would be weird since we do not have molecular analogues. --Smokefoot (talk) 18:04, 13 May 2015 (UTC)Reply