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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Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part II. Ore deposits

Collection:: Economics Books

nd ‘en ed til vol. be he ite ed arf he Jl «ch he to gn ig. rat ke :h- B- ig ce. ed ar- te. le- re ng {o- iy to te, yb- ars he ler ies na. ORES OF GOLD ve lanes ; Some of the mines are in rocks silicified hE shear sands others were probably bedded rerruginous rocks containing altered to ironstone and quartzite. T ot of Upper Palxo- the ores disappear to the N. beneath a shee lance, by tracing Zoic sandstone. Survey by the torsion nae, the course the buried granite and basic rocks, werd oo Gold-bearing of any northern extension of the goldfie inners Sorice focks outcrop further N. in Pilbara with a San similar to the Ad conglomerg tog that have been describe ld in these con- Banket of the Transvaal ; the alluvial ge of the West glomerates Suggests the pre-Cambrian ag Australigy ores 51 SEerion B. SECONDARY ORES AND ENRICHMENTS Mz. Morgay, QUEENSLAND—The early development of gold Mining wag hampered by the belief that gold would 20t be found fur below the surface. This view was Suggested by the rapid decrease in value of many gold oreg when followed downward. This fall in grade 'S In many cages due to secondary enrichment (cf. p. 31) Which hag concentrated near the surface gold that had been Spread through a great vertical range of lode. This secondary orichment jg Most marked in countries which have remained Soe sea-level for long periods of time, such as West Aus- tralia apg Southern India, In some of these fields the deeper Part of lodes which are rich at the outcrop are too low grade to Pay. An extreme case was that of the London- derry Mine of Coolgardie. A hole 2% feet deep, 6 feet long, and 5 feet wide showed £30,000 of gold; the claim was sold for £180,000, and floated as a company in London for £700,000." “Tp pocket” (Rickard, Eng. and Min, Fourn,, I6 April, 1808) “did not continue even one foot lower,” The vein below was repeatedly explored, but without Success, . Secondary enrichment on a greater scale has formed some Mportant mines, such as the Mt. Morgan Mine in Southern Queenslang. The mine was opened on a hill 400 feet high, S0mposed of 4 mass of quartz so cavernous and stalactitic that It was described by Jack as the sinter of an ancient geyser, Festing on slate and quartzite, Hot waters had leached the

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