(1) The silica, alumina , and iron come from sand, clay, and iron ore.(2) He derived the name from the mineral called alumina , which itself had only been named in English by the chemist Joseph Black in 1790.(3) The major exports are bauxite, alumina , gold, and diamonds.(4) The metals are dispersed as tiny particles on a supporting framework of porous aluminium oxide .(5) Already some sites yield little more than a mass of crystallised aluminium oxide .
