46 A. Hague — Leucite Hock in Wyoming Territory. 





No. 1. 



No. 2. 



No 3. 



No. 4. 



Silica 



47-28 



•88 



11-56 



352 



5-71 



■13 



9-20 



13-17 



2-73 



2-17 



•18 



•59 



54-42 



13-37 



■61 



3-52 



4.38 



6-37 



1-60 



10-73 



52-11 



•16 

 2301 

 8-41 

 1-75 

 trace 

 3 40 

 2-18 

 3-10 

 537 



44-35 



Titanic acid . 





Ferric oxide 



10-20 

 13-50 



Ferrous oxide 





Manganous oxide . . . 





Lime 



1T47 



Magnesia 



Soda 



12-31 

 3-37 



Potash. . 



4'42 



Chlorine 





Phosphoric acid 





•19 





Carbonic acid 



1-82 

 2-76 





Water .... . 



2-96 



1-10 









Less for CI 



100-08 

 •04 



99-58 



100-78 





Total.. 



100-04 



99-62 



No. 1, Ishawooa Canon, Wyoming Territory; No. 2, Cerrode 

 las Yirginas, Lower California ; No. 3, Leucite hills, Wyoming 

 Territory; No. 4, Bongsberg, near Pelm in the Eifel. 



The analysis of the bowlder from Ishawooa Cafion shows a 

 somewhat exceptional magma and affords a striking example of 

 a rock whose chemical composition gives but slight indication 

 of its mineral composition. No one would be led to suspect 

 the presence of leucite in a rock carrying so low a percentage 

 of alkalies. In most rocks characterized by the presence of 

 leucite, the mineral has crystallized out of a strongly alkaline 

 magma, and one in which potash is usually considerably in 

 excess of the soda as shown in the Yesuvian lavas and those 

 from the Leucite Hills. In the case of the Ishawooa rock the 

 soda and potash taken together only sum up about five per cent 

 of alkali with soda in excess of the potash The amount of 

 magnesia present is exceptionally high with a correspondingly 

 low amount of alumina, in this respect quite unlike the 

 Yesuvian leucite-basalts. It is evident from a study of this 

 olivine-leucite-phonolite that the olivine, augite, magnetite and 

 apatite were the product of the first generation of crystals 

 and were developed out of the magma before the crystal- 

 lization of the orthoclase and leucite. Now by removing from 

 the original magma the material required for the earlier crys- 

 tallization there would remain a magma carrying in a more con- 

 centrated form the greater part of the alkalies, which as shown 

 by the second generation of crystals, was more favorable for 

 the development of orthoclase and leucite. It is a marked 

 instance of the potassium and sodium silicates being the last to 

 solidify. Under different conditions of crystallization a mineral 

 development quite at variance with that found in this rock 



