The Elements of economic geology

Bibliographic data

Monograph

Identifikator:: 1773832379

URN:: urn:nbn:de:zbw-retromon-172798

Document type:: Monograph

Author:: Gregory, John W. http://d-nb.info/gnd/11683014X

Title:: The Elements of economic geology

Place of publication:: London

Publisher:: Methuen

Year of publication:: 1928

Scope:: XIV, 312 S.; graph. Darst.

Digitisation:: 2021

Collection:: Economics Books

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Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part II. Ore deposits

Collection:: Economics Books

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

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