THE auriferous sulphide ores of the eastern end of Gippsland, and notably of the Cassilis and Mitta districts, are amongst the most complex and refractory in Victoria-perhaps in Australia. The minerals occurring in these ores are pyrite, arseno-pyrite, zincblende, galena, and (in smaller amounts) some of the copper sulphides, as chalcopyrite and covellite; and some of the antimonial minerals, notably stibnite and jamiesonite. In the oxidized portions of the lodes, the oxidized lead and iron minerals, and small amounts of the hydrated arseniate of iron, are found. In the Cassilis mine, near Omeo, copper is present usually in quantities of under 9 %. The magnetic sulphide of iron is of fairly common occurrence. In the upper levels of the Cassilis mine tin was usually present, the amount going up to 3 % in some samples of concentrates.