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 V. Mineral fuels

Collection:: Economics Books

262 ECONOMIC GEOLOGY as the deltas of the Ganges and Irrawadi. It is also formed in swamps and shallow pools in coastal plains, such as the Dismal Swamp of Virginia where it is forming over an area of 1000 square miles. Swamp peat may contain but little earthy material or ash, because the streams are filtered by a fringe of vegetation, and only sediment blown in by the wind reaches the middle ; such peat may pass on the margin into mud. Tropical forests produce beds of decayed vegetation, as beneath their canopy of foliage the sodden undergrowth and fallen leaves and branches form forest peat. Peat in its raw state contains from 20 to 90 per cent. of water and usually about 80 per cent.; the amount may be reduced to about 20 per cent, by air-drying. Owing to the cost of handling and drying, peat is not an economical fuel, but being often low in sulphur, may be made into sulphur- low briquettes. It often contains from 1 to 2 per cent. of nitrogen which may be recovered as ammonia. Moderate pressure renders peat dark brown and tough like lignite ; pressure alone, even of 6000 atmospheres, has but little further effect, unless accompanied by a considerable rise of temperature, when peat is made hard and brittle like coal. LieNITE OR BROWN Coar—Lignite or brown coal is dark brown and tough, and often shows woody fibres. It has no regular jointing, but splits into layers and weathers with curved or flat surfaces. It generally contains from 10 to 35 per cent. of moisture; a little pyrites is usually present, and the amount may be large. Lignite is light in weight (sp. gr. up to 1:3). The fixed carbon varies from 15 to 50 per cent., the volatile constituents from 25 to 50 per cent, and the nitrogen is usually about 1 per cent.; when freed of ash and moisture its heat-giving value is from 10,000 to 12,000 B.T.U. Its main defect as fuel is that it readily falls to powder; so much is lost in transport, and as unburnt powder in the smoke. Lignite is used largely as briquettes, especially in Germany, where about 4 cubic yards of lignite, which before the War cost from a shilling to six shillings to mine, make one ton of briquettes. Brown coal deposits are sometimes of enormous thickness. A bore at Morwell in Victoria passed through 781 feet of

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