REDISTRIBUTION OF ALUMINUM. 985 



To some extent this deficiency is accounted for by the bauxite and 

 gibbsite deposits, which serve as ores of aluminum. Rather extensive 

 deposits of this kind are known in France and in the United States, in 

 Georgia, Alabama, and Arkansas. The French deposits are ascribed "by 

 Coquand and Auge" to mineral springs or geysers, which brought the 

 material of which they are composed to the surface and supplied it to lakes, 

 where it was deposited along with other sediments." 11 



Hayes has discussed the Georgia-Alabama and the Arkansas deposits. 

 The source of the Georgia-Alabama bauxite he regards as shales which 

 underlie limestones. ' These shales contain pyrite. 



It is believed that surface waters carrying oxygen in solution gained access to 

 these shales and by oxidizing the pyrites set free sulphuric acid. This, under the 

 conditions present, decomposed the aluminous shales, forming alum and sulphate of 

 aluminum. Ascending currents carried these salts in solution to the surface, and, 

 coming in contact with the limestone during their upward passage, they were decom- 

 posed, forming sulphate of lime and aluminum hydroxide, together with basic sulphate 

 of aluminum, which was subsequently changed to aluminum hydroxide on exposure 

 to the air. The aluminum hydroxide thus produced formed a gelatinous precipitate 

 which collected about vents of springs. It was kept in motion by the ascending 

 water and thus formed concentric structures. 6 



The Arkansas deposits are regarded as produced by an underground 

 circulation in a manner somewhat similar to those of Georgia and Alabama; 

 but the source from which the alumina is derived is syenite, and the springs, 

 instead of issuing on the land, issue under water, and thus the deposits 

 are somewhat more widely distributed. Many of the springs issue directly 

 above the syenite, and therefore the bauxite deposits overlie the undulating 

 syenite surface. Other springs issue through the adjacent Tertiary sediments, 

 which in such cases are overlain by the bauxite deposits. 



Bauxite deposits of character somewhat similar to those of France and 

 the United States are known in other parts of the world, but probably the 

 total amount of alumina segregated in all the known bauxite deposits is but 

 an insignificant fraction of the deficiency above calculated for the ordinary 

 sediments. 



a Hayes, C. W., Bauxite: Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 3, 1895, p. 548. 

 6 Hayes, C. W., The Arkansas bauxite deposits: Twenty-first Ann. Rept. U. S. Geol. Survey, 

 pt. 3, 1900, p. 461. 



c Hayes, cit., pp. 464-466. 



