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

[26 ECONOMIC GEOLOGY supply but uses nearly half. The Chinese output may be reduced by political disturbances; but as a civil war in China usually has a less disturbing effect on business than a general election in some countries, the Chinese mines will probably maintain their output unless there be a fall in price. Tue DistrRIBUTION AND FORMATION OF ORES—Owing to the varied chemical combinations of antimony it has a wide range in distribution, from deposition as a primary constituent in deep-seated lodes, to secondary segregations and deposits near the surface. The chief commercial mineral stibnite, Sb,S,, containing 71-4 per cent. of antimony, is either primary or secondary. Many sulphides of antimony with lead, copper, and silver are also primary. The chief secondary minerals of commercial value are the oxides ; they are some- times associated with native antimony that has been formed by the reduction of sulphides or oxides. Stibnite is a deep- seated primary mineral in the tin-tungsten lodes of Bolivia, in gold-quartz in Bendigo in Victoria, in the Phoenix Mine at 2300 feet in Rhodesia, and in the silver-lead veins of the Harz Mountains and of British Columbia. That stibnite has also been deposited as one of the later sulphides is shown by its occurrence in cross-course veins, as in Cornwall. The main supplies of antimony come from shallow secondary de- posits of stibnite, of which the distribution is similar to that of mercury. The characteristic occurrence of stibnite is in large nodular or kidney-shaped masses often with a radial structure. They reach the size of 3000 Ib. in sandstone in southern Utah; 2300 Ib. in granite in Bohemia ; 1200 Ib. in the upper part of the Cornish copper lodes; and 500 Ib. in Arkansas ; large masses also occur in California, and at Whroo in Vic- toria; an incomplete stage of segregation is represented by the irregular bunches of ore in New South Wales. The prolific antimony deposits in China are due to secon- dary concentrations near the surface. The most important mine is at Hsi-K'uang Shan in Hunan (Tegengren, Geol. Surv. China, Bull. iii, 1021, pp. 1-25). The field consists of Silurian, Devonian, and Carboniferous rocks, which have been compressed into folds and traversed by innumerable cross- iractures. The sandstones have been shattered and the

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