Rio Tinto's 100 per cent owned subsidiary, Comalco, is a major Australian based supplier of bauxite, alumina and primary aluminium to world markets. It employs approximately 3,300 people. Approximately 90 per cent of the bauxite from Comalco's wholly owned Weipa bauxite mine is shipped to its alumina refineries in Gladstone, Queensland and Sardinia, Italy, in which Comalco has consortium interests. Comalco's smelter's at Bell Bay (100 per cent) and Boyne Island (59 per cent) in Australia and Tiwai Point (79 per cent), New Zealand produce primary aluminium. Boyne Island is one of the largest and most efficient smelters in the world. It has an annual rated capacity of approximately 500,000 tonnes. Comalco supplies bauxite for its own requirements as well as those of other participants in the refineries under long term contract. More than half of its aluminium production is exported from Australia and New Zealand, mainly to Japan, Korea, Taiwan, Thailand, Indonesia and other southern Asian destinations. Weipa also produces calcinated bauxite for abrasives, which is exported, mainly to the US and Europe.