The petro-graphical definition of bauxite is a chemical weathering product, an ore that contains a minimum of 50% of alumina hydroxides. In order for the bauxite to be designated commercial grade, extracting the alumina must be economical. More than 90% of the world's bauxite reserves, called laterite bauxites, are concentrated in tropical and subtropical regions from approximately 60 million years ago.
Large deposits are found in Australia, South-East Asia, South America and India. They are located beneath the surface and are extracted through the open pit mining method. In the Caribbean, as well as in Southern Europe, bauxite is found in smaller pocket deposits where they accumulated on carbonate rocks to form bauxites.
Although demands for bauxite are growing, China is optimistic about its continued availability. Bauxite deposits might be about 70 billion tons. We'd probably be able to process about half of that - the rest would be too difficult to get to without significant improvement of the infrastructure. The world consumed about 260 to 270 metric tons last year. At that rate of consumption, we should be able to meet our demands for the next 250-300 years.
The process for mining bauxite is not complex. Unlike ores from base metals, the grade of most bauxite found through mining is acceptable. Bauxites of Brazil, South-East Asia, as well as some types found in Australia and China, need up-grading from the crude ore. This is achieved by washing and screening, and then the super-fine fractions (clayey components) are removed. The yield of the concentrate (industrial grade ore) is between 40 and 60%.