The Elements of economic geology

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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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Document type:: Monograph

Structure type:: Chapter

Title:: Part II. Ore deposits

Collection:: Economics Books

ORES OF COPPER 81 per cent. of the total and is exceeded by that of seventeen other countries. The price of copper undergoes great variations, which make or mar the fortunes of mining fields. The price of English tough copper (994 per cent. of copper; standard copper, now generally quoted, has 96 per cent.), was £160 a ton from 1801-10; the price fell to £55 between 1891-1900; it rose to £127 in 1017, but since the War it has again fallen, and early in 1927 was below £35. The fall in price has been due to the increased output especially from America. In 1801-10 Russia was the second Producer with 18 per cent. of the total. Australia, towards the middle of the last century, was the third producer, but its output has fallen by two-thirds. The United States now provides sometimes 75 per cent of the world’s output, the test coming mainly from Chile, Africa (owing to the growing production from Katanga in the Congo basin), Portugal, Peru, and Australasia. The world's production in 1890 was 260,000 tons; the record, 1,415,000 tons, was in 1917 owing to the demands of the War, after which there was a serious decline; the output has again increased to a little over 1,400,000 tons in 1925. CrassiFicaTioN oF ORES Copper deposits may be divided into four chief groups— Primary lodes, replacement ores, secondary enrichments, and sedimentary ores; the classification is difficult and in- definite as the copper minerals, being easily soluble, are liable fo" concentration by repeated solution and redeposition. Primary and secondary ores often occur in the same mine. The value of many mines depends on the secondary enrich- ments, the primary ores being of low grade. The copper ores may be classified as follows :— SECT. A. Primary OrEs— L Primary Lodes— (2) Pneumatolytic—(1) Svartdal, Norway ; Vogtland, Saxony; Rossland; Burra-burra; (2) in vol- canic pipe—Braden, Chile. (6) Quartz-lodes. Cornwall. (c) Pipe-lodes and shoots. Wallaroo; Namaqualand. 3

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