Page 11 - Curriculum Visions Dynamic Book

feldspar: a mineral consisting of sheets of aluminium silicate. This is the mineral from which the clay in soils is made.
granite: an igneous rock with a high proportion of silica (usually over 65%). It has well-developed large crystals. The largest pink, grey or white crystals are feldspar.
ore: a rock containing enough of a useful substance to make mining it worthwhile.
Bauxite
The name bauxite comes from an ancient mine site at Les Baux in the south of France. Bauxite is a tropical soil material, full of clay like any other soil. Under hot, moist conditions some
of the aluminium does not get locked up as clay, but instead forms sheets of aluminium oxide.
Aluminium oxide is usually colourless or greyish-white, and often forms alongside oxides of iron under humid tropical conditions. Iron oxides are red, and their bright colour masks the pale aluminium oxide. Most bauxite is found inside the tropical red (iron-containing) subsoil material known as laterite.
To get aluminium metal from bauxite the aluminium must be separated from both the oxygen and the oxides of iron.
Modern bauxite mines are located where the ores contain at least half their volume of
aluminium oxide. All of the ores are soil layers and thus are always mined in shallow open-
cast pits. Today the majority of bauxite comes from Guinea, Australia, Jamaica
and Brazil.
The known reserves of bauxite
will last for several hundred years if the consumption can be kept
to present levels by careful recycling.
 Bauxite rock has an orange–red colour because of staining by iron oxides.
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The process of manufacturing aluminium metal from bauxite has many stages. These are described here and on the following pages.