Summary: Kornerupine, which differs from previously described material chiefly in having a higher ferric iron and lower magnesia content, is found in the Port Shepstone district, Union of South Africa. An analysis of this material shows that the composition of kornerupine varies between wider limits than hitherto known. From this and other analyses the general formula is deduced as (R2‴,R3″,R6′)3(Si3B4)O15.