Oeuvres complètes

The Elements of economic geology

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Monograph

Identifikator:: 836084659

URN:: urn:nbn:de:zbw-retromon-28892

Document type:: Monograph

Author:: Ricardo, David

Title:: Oeuvres complètes

Place of publication:: Paris

Publisher:: Guillaumin

Year of publication:: 1847

Scope:: 1 Online-Ressource (XLVIII, 752 S)

Collection:: Economics Books

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Document type:: Monograph

Structure type:: Title page

Collection:: Economics Books

CHAPTER VII ORES OF LEAD, ZINC, AND SILVER Leap—Irs Uses, etc.—Lead (Pb; at. wt, common lead, 207, uranium lead, 206 ; sp. gr., common lead, 11-33, uranium lead, 11-27; melting-point, 620° F.) is one of the six metals that was used by prehistoric man ; it is easy to work, being soft, ductile, and malleable. Among its valuable properties are its flow under pressure while’ cold, melting at a low tem- perature, and insolubility in concentrated sulphuric and hydrochloric acids. It is a constituent of some alloys in- cluding pewter, and being the heaviest of common metals is used for bullets. In 1025 40 per cent. of the supply was used by the electrical industry and 25 per cent. for paints. British lead mining was at its zenith in 1856 with 353 mines at work, and an output of 73,129 tons of lead and 61,400 oz. of silver. The price of lead was then £32 a ton. The price fell, after the opening of lead mines in the United States, Mexico, and Australia, to as low as £13 16s. per ton in 1896. The United States has in recent years supplied 40 per cent., Mexico 11 per .cent., Spain 10 per cent., and Australia 10 per cent. of the world’s output. The British Isles in 1924 produced only 10,863 tons, mainly from eight mines. The declining yield of the six chief mining fields has led to the price rising to £40 per ton in 1924, but it has fallen again to £28 in 1927. Native lead is rare, as it is slowly oxidized, but it has been often recorded from torn shot found in gravels. The chief lead mineral is galena (PbS), which is usually associated with blende (ZnS), and nearlv alwavs contains silver as argentite (Ag,S). CrassiFicatioNn oF OrRes—The primary lodes occur along faults and fractures. Those due to the filling of fissures are often well crustified. Many lodes that are productive in ab

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