Smaltite

Originally considered to be a cobalt diarsenide, with postulated formula CoAs_(2-2.5), then reclassified as an arsenic-deficient variety of skutterudite, CoAs_{(3-x, x ~0.35)}, but this non-stoichiometry may not be significant as old analyses may generally be due to mixtures, so it is probably best considered a synonym for skutterudite, close to CoAs₃.

Lewis S. Ramsdell (1925) studied smaltite and chloanthite, but did not solve the problem of the chemistry of the series. Ivar Oftedal (1926) reached the conclusion that smaltite and chloanthite formed a series that was non-stoichiometric (As-deficient), but with the skutterudite structure. Holmes (1947) synthesised many Co-Ni-Fe arsenides and reviewed the historically published chemical analyses of these and found no support for significantly non-stoichiometric compositions of any smaltite, skutterudite, chloanthite, etc., and considered the apparent non-stoichiometry of their analyses to be due to mixtures of various orthorhombic and isometric arsenides. He described chloanthite and smaltite as synonyms of skutterudite. Roseboom (1962) also synthesized and studied skutterudites and established their chemical variations and again found no support for any non-stoichiometric compositions, and also described all the triarsenides as skutterudite. Oen et al. (1984) studied white arsenide paragenesis and summarized previous studies.