W. C?*oss — Igneous Rocks in Wyoming. 



133 



to potash the same. By tbe calculation of the Boar's Tusk 

 rock it would seem necessary to assume that the hypothetical 

 mineral had the composition of orthoclase. No such mineral 

 being known, this hypothesis would quickly lose all suggestion 

 of support were it not for the results derived from a calcula- 

 tion of the analysis TV. 



Calculation of Analysis IV. 





Molec. ratio. 1 Apatite. 1 Diopside. Phlogopite. 



Leucite. 



Residue. 



Si0 2 895 



Ti0 2 24 



. 



76 

 2 



2 



37 

 39 



144 



6 



22 



3 



3 



122 

 25 



348 



87 



87 



327 

 16 



A1 2 3 109 



FeoOs 20 



FeO 17 



CaO 71 



MgO 161 



K 2 119 



39 

 12 





 17 

 12 

 

 

 7 



Na 2 27 



P 2 5 12 



27 

 







| 



\6-1fc 



22-3$ 



35-7$ 





The calculation shows a marked excess of the alkalis and a 

 very large one of silica. In this case the sulphuric acid is so 

 low as to be of little effect upon the calculation in assuming it 

 to represent noselite. Here, then, as before, there is an appar- 

 ent excess of silica which cannot be discovered in the rock in 

 the form of opal, tridymite, or quartz, and the excess of alkali 

 is equally difficult of explanation. Alumina cannot be assumed 

 as too low by error of analysis, as the analyses are quite con- 

 sistent in this respect and repeated determinations have yielded 

 almost identical results, as also in the case of S0 3 . 



Acting upon the suggestion that the apparent leucite of 

 these rocks might possibly have a different composition from 

 the normal, Dr. Hillebrand treated the powder of the wyoming- 

 ite yielding the result under IV with dilute nitric acid (1 acid 



r) and tor 



md in soluti 



on the ioll( 



)wvng : 



Molec. ratio 



Si0 2 ___. 





... 6-08 



101 



Ti0 2 .__. 





... '21 



3 



Al . _ . 





... -91 



9 



FeO* ... 





... -50 





CaO .... 





. . . 2-13 



38 



SrO .... 





. .. -10 





BaO .... 





... "14 





MgO.... 





... 1*51 



38 



K O 





. .. 1-21 



13 



-*■ 2 ^ 

 Na,0... 





•28 



4 



P.O.—- 





. .. 1-54 



11 





14-61 







* All iron 



as FeO. 





Am. Jour. Sci.— Fourth Series, Yol. IV, No. 20. — August, 1897. 

 10 



