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 LEAD, ZINC, AND SILVER 109 Stone, or limestone. The ores at Ceeur d'Alene in Idaho and Leadville in Colorado, for example, are remarkably alike, in SPite of the difference in structure between, the two fields. This similarity indicates that the ores are not derived from ither the adjacent sedimentary or intrusive rocks, but ‘Ome from an ore-zone beneath the igneous rocks of the ‘rust. Like the plutonic waters they work their way up- Vard through igneous and sedimentary rocks alike. ZINC Zivc (Zn ; at. wt, 65; sp. gr, 71; melting-point, 790° F. ; volatilizing-point, 1520° F.) is a comparatively modern metal ‘0 the western world, though it has been long used by the Chinese. The origin of the name is uncertain, but is probably from #inn, the Greek for tin. Spelter, the trade name for the metal, was used in Germany and Spain for the alloy Pewter. Zinc is bluish-white, brittle when cold, but malle- able when hot. Most of it is used for galvanizing iron as a Protection against rust; its other chief uses are as white Paint, a drug, and in many alloys, such as German silver, which is composed of nickel, zinc, and copper. The price of nc before the War was generally about £22 a ton; it rose to £100 a ton in 1015, after which it fell to £52 and early in 1927 was about £30. The bulk of the zinc ores comes, in order of quantity, from Germany, Australia, the United States, Italy, ang Spain. The zinc is seldom extracted at the mines, and the largest production of spelter is in the United States, Belgium, ang Germany. Belgium was the home of this ‘ndustry which is now threatened by the electrical pro- cesses of zine extraction. The common ore is blende (or sphalerite, ZnS), which is constantly associated with galena, and most zinc is obtained from lead ores. FrankLin OrEs—1In the secondary ores lead and zinc are often Separated, and the zinc is frequently deposited in con- Centric layers known as schalenblende. Some secondary Ores are of special value as free from lead. Thus at Franklin, New Jersey, a trough-shaped sheet of ore in a pre-Cambrian limestone includes willemite (ZnSi0,), zincite (ZnO), and franklinite (oxide of zinc, iron, and manganese). The origin of this deposit js a vexed question. The absence of lead suggests that the ore is secondary. It has probably been formed by

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