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 V. Mineral fuels

Collection:: Economics Books

COAL AND ITS CLASSIFICATION 267 5 of nel ly the 1as 30 or sh. the ns ate 1b- 21l- us nd ies tal ar- he er nt. nt, he ad sh wt 1S 1341 1d of of 1, 3. and hydrogenous or gas coal. In the last division he in- cluded cannel, torbanite, and * asphaltic coal” or albertite, a fossil bitumen. Rogers’ classification was based on the ratio of fixed carbon to volatile matter—the bituminous coals containing from 52 to 84 per cent. of fixed carbon and 12 to 48 per cent. of volatile matter, and anthracite contain- ing 84 per cent. of fixed carbon and 7} per cent. of volatile constituents. This system was developed by Persifor Fraser (2nd Geol. Surv. Pennsylvania, MM, 1879, pp. 143-4), who adopted the same divisions and based them on the ratio of fixed carbon to volatile hydrocarbons, the ratios being in anthracite 100: 12, in semi-anthracite 100: 67, in semi- bituminous (including dry steam coals) 100: 62; in bitu- minous between 100: 106 and 100: 25. Classifications based on the ratio of carbon to hydrogen have been adopted by Campbell of the United States Geolo- gical Survey; and C. H. Seyler for the coals of South Wales (Proc. S. Wales 1.E., 1900, xxi, p. 483 ; xxii, p. 112). Seyler’s five divisions are based on the percentage of hydrogen— namely perbituminous with hydrogen more than 5-8 per cent., bituminous 5% to 5:8 per cent., semi-bituminous 4} to 5 per cent., carbonaceous 4 to 4} per cent., and the anthracitic less than 4; each division is subdivided according to the carbon percentage. This classification well illustrates the con- tinuity of the coal series from lignite to anthracite, but is too elaborate for general commercial use. A classification based on both physical and chemical properties has been adopted in the volumes on the Coal Resources of the World, issued by the International Geological Congress, 1913, i, pp. Xi-xiii. Tue Origin oF Coar—Coal is generally regarded as the fossilized debris of ancient forests; most coal contains so little wood that many authorities, such as Jeffreys, Lomax, Hickling and Murray Stewart, have returned to the view of Hutton in the eighteenth century, that coal was deposited as a fine-grained carbonaceous silt carried by rivers to lakes or the sea, or as a humic jelly or as sapropel, an organic mud. Another explanation—of historic interest as it was supported by Darwin and Huxley—was that coal is an injection along some permeable layer of liquid bitumen, which has incorpor- ated the remains of plants. Some coal has been formed in situ from the vegetation

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