This paper discusses the applicability of polarization figures and rotation properties to the identification of the sulfarsenides of cobalt, nickel and iron in polished surfaces. The rotation properties of these minerals have been determined and are summarized here. These properties offer a valuable new aid to the identification of the anisotropic sulfarsenides of cobalt, nickel and iron. They do not assist materially in the identification of the isotropic minerals investigated. Oil immersion techniques are not of great value in facilitating identification, but a special application of immersion methods is suggested by studies of the safflorite-loellingite series.