ANALYSES OF BENTONITE AND LEVERRIERITE 615 



1 3) Bentonite from Birmingham, Alabama, "Twentieth Street and Red 

 Mountain cut ; bentonite, 19 inches" ; analysis by D. F. Farrar. 



(4)- Bentonite from Birmingham, Alabama ; "Woodward shaft, east of 

 Readers, at a depth of 1,300 feet ; analysis by D. F. Farrar. 



(5) Bentonite from eight miles south of Buffalo Gap, South Dakota; Wash- 

 ington Academy of Science, volume 7, 1917, page 580; analysis by Edgar T. 

 Wherry. 



(6) Bentonite Laramie basin, Wyoming, Cosgriff's claim. 



(7) Bentonite, Laramie basin, Wyoming, Cassa Mining Company. 



(8) Leverrierite from Beidel, Colorado; from Washington Academy of 

 Science, volume 7, 1917, page 213 ; analysis by E. T. Wherry. 



A new Theory of the Formation of Bauxite Deposits 



Experiments made on bentonite show that when boiled with a five times 

 normal solution of sulphuric acid for five hours the colloidal properties 

 are destroyed; that about 85 per cent of the aluminum oxide goes into 

 solution as aluminum sulphate, along with the alkalies present, but that 

 all the silica except a trace remained undissolved. This fact offers a 

 possible solution to the origin of bauxite, as laboratory experiments show 

 that such a solution of aluminum sulphate is precipitated by a solution 

 of tannic acid after standing for a few days. Deposits of bentonite oc- 

 curring in contact with pyritiferous rocks would readily have part of 

 their aluminum contents dissolved out by the sulphuric acid in the 

 ground-water, and such a solution of aluminum sulphate, it seems, would 

 be precipitated by natural reducing agents, such as tannic acid or acid 

 peat-forming bacteria, and thus form certain of our present bauxite 

 deposits. 



