270 J. C. BR ANNE R 



10. I south, 13 west, section 10, southeast quarter of the 

 northwest quarter. 



11. Baux, near Arle, France (Sainte-Claire Deville) . 



12. Revest, near Toulon, France (Sainte-Claire Deville). 



13. Near Feistritz, Styria. 



The analysis must determine the value of bauxite, but it 

 should not be forgotten that varieties not available for one pur- 

 pose may sometimes be used for some other purpose. As a rule, 

 however, silica, iron, and titanium are the objectionable ingre- 

 dients. When the percentage of silica reaches that in kaolin or 

 clay the bauxite has no advantage over kaolin or clay for the 

 purposes for which it is used. 



Mr. McCalley, in his valuable paper upon Alabama bauxite, 

 calls attention to the fact that the surface material contains more 

 silica than samples taken at a depth.' This had escaped atten- 

 tion in my brief examination of the Arkansas bauxite, but since 

 reading Mr. McCalley's paper I recall the fact that this view is 

 borne out by the analyses of the Arkansas materials so far as they 

 have been made. If this is a fact that can be depended upon 

 as constant, it is one of great importance in mining bauxite. 



In the ferruginous, earthy, and kaolin-like varieties the piso- 

 litic structure is always more or less pronounced in the Arkansas 

 bauxite. 



Structure and appeara^ice. — Bauxite is very light ; its specific 

 gravity is about 2.4. In gross structure, color, texture, and 

 general appearance Arkansas bauxite varies greatly. The colors 

 are red, pink, brown, black, gray of various shades, white and 

 yellow, and these colors are also more or less mixed in the same 

 deposit, and even in the same hand specimen. 



The several classifications or subdivisions proposed by 

 Coquand, Laur and others will, in all probability, hold with the 

 Arkansas deposits, but inasmuch as these divisions all grade 

 insensibly into each other it seems unnecessary to give those 

 classifications or to lay any stress upon them. Chemical analyses 

 and the practical availability of the different varieties can alone be 



'Proc. Ala. Ind. and Sci. Soc, Vol. II, 1892, p. 29. 



