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 IRON 147 Boe Iron Ores—The famous microscopist, Ehrenberg, described as Gaillionella ferruginea, a fresh-water alga with stems charged with hydrous iron oxide, which has been regarded as a normal secretion of the living organism like the carbonate of lime in shells and coral. A. Gages has described a mould, Penicillium, that grew in the tanks of the College of Science, Dublin, and extracted so much iron that if burnt it left a skeleton of hydrous iron oxide. Ac- cording to some authorities the deposition of the iron oxide in these plants is a post-mortem process due to the reduction of iron salts by the decomposing tissues. According to D. Ellis (Iron Bacteria, 1919, pp. 191-2, p. xvii, etc.) the living iron bacteria secrete iron directly and thus help the formation of bog iron ore; but according to H. Mélisch (Pflanze in Bezichungen zum Eisen, 1892, p. 80) their contribution is insignificant, and usually nothing. Bog iron ore though of good quality occurs in comparatively small quantities. The most important deposits were those in the Swedish lakes which are renewed and re-dredged at in- tervals. Larger masses occur in many parts of the world, such as the Hill of the Pines, or Mesa de los Pinos, at Rio Tinto ; it contains fossil leaves and was deposited in a swamp from iron derived from the adjacent masses of pyrites. SURFACE ORrES—EFFLORESCENT, RESIDUAL, AND ALLUVIAL Ores—Superficial sheets of iron ore are widespread. They occur as residual deposits left by the solution of limestone as in Franconia; as a sheet of spherosiderite or crust of hematite which breaks up into ironstone or “crowfoot gravel, over weathered basalt; as crusts or concretions of ironstone formed as efflorescent deposits over sandstones or sands; as laterites due to evaporation during the dry season of water which has soaked into iron-bearing aluminous beds ; as the sheets of nodular hezmatites in some of the rich ores in Bengal. These ores are high in phosphorus, usually ranging from 2 to 2 per cent., and are low in titanium, Alluvial iron ores are concentrates of iron oxides on river beds and sea beaches, such as the black iron sands due to the disintegration of igneous rocks containing magnetite, These black sands are collected in alluvial mining, but as the magnetite is titaniferous they have hitherto been of no commercial value, though they may be useful now that titan- lum oxide is used as a paint.

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