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 III. Earthy minerals

Collection:: Economics Books

204 ECONOMIC GEOLOGY and fish. True coprolites are usually cylindrical or ovoid in form, and have a spiral mark impressed by the wall of the intestine. The bulk, however, of the coprolites used by the phosphate industry are concretionary nodules which may derive their phosphoric acid from either bones or dung. Such lagoon and nodular deposits are represented by the coprolite beds of the East of England, and among the phos- phates of Florida, and South Carolina, on the coast of the Unites States. Some of the American coastal phosphates may have been formed by the alteration of limestone reefs or islands from deposits of guano. Some lagoons were underlain by limestone which has been phosphatized by acid from above. This phosphate usually occurs in isolated masses and hummocks, owing to the ir- regularity with which the phosphoric solutions percolated through the overlying deposits or penetrated the limestone. The American coastal phosphates in 1925 yielded 3,000,000 tons. GRANULAR PHOSPHATES AND PHOSPHATIC CaaLr—Granular phosphatic limestones and phosphatic chalk represent another important source of phosphate. The phosphoric acid in sea-water may act upon the microscopic shells of dead organ- isms and convert them into phosphate of lime either in their fall through the sea-water or while lying on the sea-floor. In most marine deposits the proportion of phosphatized shells is small, but on shoals and parts of the sea-bed swept by strong currents, the calcareous organisms may be broken up and removed, while the harder and less soluble phosphatic shells remain as layers of granular phosphate. Layers of phosphatic chalk occur in the English chalk as at Taplow ; in the North of France and Belgium this process has pro- duced larger beds which supported the phosphate industries of those countries. Some of the more massive occurrences, as in the Somme valley, have been attributed to mineral springs. In warmer seas the process has formed thick beds of limestone charged with granular phosphate in Algeria, Tunis, and parts of Egypt. The Carboniferous Limestone of the Rocky Mountains belong to this group, and include large reserves of granular phosphates which are too remote from fields where fertilizers are required to be worked profitably at oresent,

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