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 I. Introduction

Collection:: Economics Books

ECONOMIC GEOLOGY the pure water necessary to its health. In addition to the study of these materials, the economic geologist is concerned with the arrangement of rocks to facilitate their quarrying, with the protection of coasts from attack by the sea, of plains from devastation by rivers, of harbours from shoaling, and of buildings from overthrow by earthquakes, with the avoidance of hidden dangers in the selection of reservoir sites, and the maintenance of public health by the utilization of underground water and safe methods of drainage. The problems of economic geology are complex owing to the multiplicity of the materials, the variability of local conditions, and the influence of prices and costs. A material which in one place may be a valuable ore in another may be commercially worthless. Profitable use is an essential factor in the definition of the term ore. An ore is a material con- taining sufficient metal to be worth mining under conditions which either already exist at the locality, or may be reason- ably expected. MiNERAL—This term is used with two different meanings. Mineral in the general sense is any inorganic material, and includes animal and vegetable products which have been buried in the earth and become part of its crust. Some geologists limit the term to materials which have a definite chemical composition, and usually a regular crystalline shape, and regard coal, slate, limestone, mineral oil, oil shale, and most ores as not minerals. The aim of this inconvenient definition is to emphasize the distinction between simple minerals and rocks. Before about 1850, rocks were regarded as minerals ; the first editions of Dana’s System of Mineralogy included a chapter on “Rocks or Mineral Aggregates.” Lyell (Principles of Geology, 7th ed., 1847, p. 784) distin- guished between * simple minerals ” and mineral aggregates. Minerals were divided into two sections; simple minerals, or mineral species, such as quartz and felspar, cannot be divided into simpler constituents without chemical decom- position ; compound or mixed minerals may be separated into their components mechanically, as granite can be separ- ated into its three mineral species, quartz, felspar, and mica, by crushing and sorting the fragments. As academic mineralogy developed it was limited to the study of mineral species, and most compound minerals were left to the branch

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