ANALYSES 



Complete Analysis 



Per cent 



SiO, 88.28 



AUO3 7.92 



Fe.Oa 88 



TiOa l'<6 



Screen Test 



Per cent 



Plus 60 mesh equals 1-15 



— 60 plus 80 equals 6.26 



— 80 plus 100 equals T.98 



— 100 plus 200 equals 24.86 



— 200 equals 59.75 



535 



100.00 



The presence of lignite intimately associated with the kaolin and 

 bauxite of the Isabella Stewart mine shows that the bauxite was depos- 

 ited just before swamp conditions existed on the edge of this old pene- 

 plain, and shows conclusively that the bauxite was formed on such an 

 old peneplain probably just before the end of this baseleveling period 

 and just before a slight subsidence which permitted the accumulation of 

 the lignite. 



According to Hayes,^ the Appalachian deposits, of which the above is 

 a typical example, were formed imbedded in residual clay derived from 

 the weathering of limestone. His resume of this theory is as follows : 



"The limestone overlies a great mass of shales (lying 500 to 4,000 feet below 

 the surface), and the formations are intersected by numerous faults, along 

 which water has in the past found easy access to great depths. The shales 

 are made up largely of silicate of aluminum. They also contain considerable 

 iron sulphide in the form of pyrites. It is believed that the 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, de- 

 composed 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 hydrox- 

 ide on exposure to the air. The aluminum hydroxide thus produced formed 

 a gelatinous precipitate which collected about vents of springs. It wa"s kept 

 in motion by the ascending water and thus formed concentric structures. The 

 reactions indicated above are all known to take place in nature and the process 

 is one which is readily understood." 



» C. W. Hayes : Twenty-first Annual Report, U. S. Greol. Survey, part iii, 1809-1900. 

 p. 461. 



