210 



THE CRYSTAL FALLS IRON-BEARING DISTRICT. 



morphosed form of clay slate; Nos. 2 aud 3 are tlie intermediate phase, aud 

 No. 4 is the most metamorphosed phase. 



Comparison of analyses of clay slate, spilosites, and adinole. 



XHjO at 110°. 



+H;0 above 110°. 



No. l = Clay slate (Sp. 32497). Sec. 17, T. 43 N., K. 31 AV., 450 N., 1620 AV.; George Steiger. 



No. 2 = Spilo8ite (Sp. 32861). Sec. 7, T. 43 N., E. 31 AV., 750 N., 1380 AA^ ; H. N. Stokes. 



No. 3=Spilosit6 (Sp. 32827). Sec. 7, T. 43 N., R. 31 AV., 250 N., 325 AV. ; H. N. Stokes. 



No. 4 = Adinole (Sp. 32465). Sec. 8, T. 43 N., E. 31 AV., 500 N.,475 AV. ; George Steiger. 



In these anah'ses the usual increase of silica as the dolerite is 

 approached is at once noticeable, and hand in hand with it goes the diminu- 

 tion in percentage of alumina and iron oxides. The content of water and 

 carbonaceous matter also suffers a diminution. The most noteAvorthy differ- 

 ence between the claA' slate and the contact rocks is shoAvii in the relations 

 of potassa and soda. This is well brought out in an examination of analyses 

 Nos. 1 and 2. It Avill be seen that there is only about one-eighth as much 

 potassa in the contact rocks as in the normal clay slate; Avhile, on the con- 



