ORES OF ALUMINIUM I55 
Bauxite is named from les Baux, near the mouth of the 
Rhone, where it occurs as a bed 30 feet thick and as pockets 
in Lower Cretaceous ; it is high in silica and alumina, and is 
used for the manufacture of alum, while the detrital bauxite 
of the adjacent district of the Var, being low in silica, is 
extensively used for the extraction of aluminium. Bauxite is 
abundant in Southern Europe from Spain, where it has been 
formed by hydrothermal action on the Lower Eocene rocks 
of Catalonia, to Rumania, where it occurs in beds and masses 
in the Upper Jurassic limestones which have been intruded 
by granite and rhvolite and faulted and tilted by mountain 
folding. 
The United States produces the largest annual output of 
bauxite, mainly in the southern states. The transition may 
be seen in Arkansas from pisolitic bauxite to material which 
retains the structure of nepheline-syenite. Some bauxite 
has been redeposited in Kainozoic times as detrital beds, 
some of which are valuable by being very low in titanium. 
In Georgia and Alabama, bauxite occurs as masses in residual 
clay overlying the Lower Palzozoic Knox Dolomite, which 
has been turned into chert by silica being carried into it 
during the formation of the bauxite. In Georgia the Creta- 
ceous and Kainozoic beds contain bauxite which, according 
to Veitch, were clays that have been altered by descending 
alkaline waters. Some Georgian bauxite contains seams of 
pyrites deposited by solutions after the conversion of the 
original rock into bauxite. 
British Guiana is one of the chief producing countries of 
high quality bauxite, which is there due to the decomposition 
of dolerite, granite, and horneblende-schists. The high-grade 
bauxite of Mt. Ejuaneme on the Gold Coast (with 64 per cent. 
of aluminium, 25 per cent. of ferric oxide, ‘5 to 3 per cent. of 
silica, and from 1-3 to 3-6 per cent. of titanium oxide) has 
been formed from the decomposition of shale. Widespread 
deposits in other parts of Africa, India, and Western 
Australia are also due to the decav of old rocks by meteoric 
waters. 
The chief uses of bauxite are for the production of alumina 
and alum, for firebricks and furnace linings, for the filtration 
of petroleum, as after heating to between 750° and 1100° F., 
it absorbs colouring matter and sulphur, and for quick-setting