§ 33. METALS. 



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Lead. — The ores of this metal are very numerous : and the sulphuret 

 of lead, or galena, occurs in primary and secondary rocks. In 

 Derbyshire, the principal veins of lead are in the carboniferous 

 limestone. 



Copper — is found in primary and secondary rocks, and in modern 

 deposits ; it often occurs native, that is, in a pure metallic state, 

 in blocks many tons in weight : its ores, or combinations with 

 other metals and minerals, are very numerous. Cornwall is the 

 principal European repository of this metal. 



Gold — exists in granite and quartz rocks. The gold found in the 

 mud and sands of rivers has been derived from veins of that metal 

 which existed in rocks, subsequently broken up and disin- 

 tegrated : such is the origin of the auriferous sands and alluvia 

 of Kussia, which we shall presently describe. 



Silver. — This metal is found in transition and primary rocks ; often 

 native, but generally in ores associated with arsenic, cobalt, &c. 

 Sulphuret of silver (a combination of metallic silver and sulphur) 

 is the most common ore of this metal. Masses of pure silver, 

 2001bs. in weight, have been found in Norway. The rich 

 Mexican silver and gold mines are in porphyritic rocks. 



Platinum — occurs in the Ural Mountains. This metal combines 

 the lustre of gold and silver with incomparable hardness. 

 A vein has recently been discovered in metamorphic rocks, in 

 the Valley of Drac, in the Department of Isere. 



Mercury or Quicksilver — is found always liquid when in a metallic 

 state ; it is generally obtained from Cinnabar, which is a 

 sulphuret of mercury, and forms beds and veins in gneiss and 

 schist ; and in strata of the carboniferous epoch. The mines of 

 Idria in Carniola are the most productive in Europe. 



Iron. — The almost universal presence of the ores of iron, and the 

 infinite variety of its combinations, are too well known to 

 require description. Xative iron is sometimes found in rocks ; 

 but from the rapid oxidation of this metal when exposed to air 

 or moisture, it is seldom met with, except in meteoric stones 

 (ante, p. 50). 



I will concisely notice a few interesting conditions of some 

 of these metallic substances. 



33. Auriferous Alluvia of Russia. — In the highly 



valuable work of Sir E. Murchison, " The Geology of 



Eussia," there is an extremely interesting description of the 



auriferous alluvia which annually yield a vast amount of 



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