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Thanks to a A$400m federal loan, it is building one of the world’s largest alumina refineries near the coastal city of Gladstone, which it says will create hundreds of local jobs.

The tiny particles they used were made of alumina, or sapphire, and are "very hard," Dowding says.

The researchers tested a range of slags, made from demolition waste and added lime, alumina and silica.

The activated alumina helps them get within the legal limit, but fluoride levels there are still far higher than most other communities in the U.S.

Extracting the alumina leaves behind waste called red mud that is highly alkaline and can also contain toxic heavy metals such as cadmium.