CHAPTER X. 



TREATMENT OF ORES. 



Metallurgical treatment. Copper from copper pyrites and other sul- 

 phides. Lead from galena. Treatment of silver -bearing ores. 

 Gold from lodes and deposits. Concentration of ore. 



IN the laboratory metals are obtained from minerals by 

 either the wet or dry process, as briefly referred to in 

 Chap. IX. 



If a mineral be dissolved in an acid or acids (N.B. Chloride 

 of silver, tinstone, &c., are, however, nearly insoluble in 

 acids), and reagents added, precipitates result; and from 

 these the metals can, by fusion or otherwise, be obtained ; 

 or. by the addition of certain metals to certain of the solu- 

 tions, other metals can be precipitated : 



Iron precipitates lead ; 

 Iron or zinc precipitates copper ; 

 Copper, zinc, iron, lead precipitate mercury ; 

 &c., &c. 



A few of the fusion methods have already been described ; 

 but for the treatment of ores on a large scale many of the 

 processes adopted in the laboratory are too costly, and, for 

 this reason, though the principles of extraction may be the 

 same, economy is of the utmost importance. The appa- 

 ratus employed must be considered with regard to its 

 original price, durability, efficiency, portability (in some 

 instances), utility with respect to its being a labour-saving 

 apparatus, and as a means of reducing the price and quantity 

 of fuel, fluxes, and other requisites to a minimum. The 

 cheapest fluxes, such as limestone (not, however, cheap in 

 some countries where freightage is expensive), and com- 

 paratively cheap chemicals have to be used where expen- 

 sive substitutes would be out of the question. So, toe, 



