Summary: Amongst the layered basic rocks of the Carlingford complex, is a gabbro which has been contaminated by a limited amount of Carboniferous Lime-stone. The clinopyroxene (Ca₄₉Mg₃₃Fe₁₈) produced in the gabbro is similar to that found in teschenitic gabbros. Such features as the instability of olivine distinguish this contaminated tholeiitic gabbro from true alkaline types. The production of aluminous augite is discussed, and comparison is made with the basic rocks of Scawt Hill and Gunnedah. Analyses of the contaminated gabbro and contained pyroxene are given.