452 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



Analysis of femic nephelite syenite, Kr'uger alkaline body — Continued. 



Mol. 



Na 2 4-03 -065 



K a O 7-30 -078 



H 2 at 110°C -13 



H„0 above 110°C 1-49 



P 2 B . -28 -002 



C0 2 -27 



100-17 



Sp.gr 2-719 



From the microscopic study it is very probable that the titanic oxide is 

 notably higher than is shown in the foregoing table. Otherwise the chemical 

 analysis corresponds well with the optical analysis. Rough calculation has 

 shown that the garnet must be low in alumina and high in lime and iron, and 

 is thus, as already suggested by its colour, a true melanite. The appreciable 

 amounts of barium and strontium oxides suggest that some of the feldspar 

 mixtures may in complexity rival the phenocrysts of the Rock Creek rhomb- 

 porphyry. We have here one more illustration of the rule that these two oxides 

 tend to occur in relatively high proportion in the highly alkaline rocks. 

 The norm calculated from the analysis is: — 



Orthoclase .\ .. 43-37 



Albite 11-00 



Anorthite 11-95 



Nephelite 12-50 



Diopside.. .' 10-80 



Wollastoni+e -70 



Magnetite 6-73 



Ilmenite .15 



Hematite -16 



Apatite -62 



Water 1-62 



99-60 

 The mode (Rosiwal method) is approximately: — 



Feldspar 63-9 



Nephelite 15-1 



Biotite Ill 



Melanite 8-8 



Apatite -6 



Titanite -5 



1000 

 In the Norm classification this rock must be classified with the first speci- 

 men as borolanose. In the older classification it may be best named a biotite- 

 melanite-nephelite syenite, transitional to malignite. 



Nephelijte Syenite. — The third specimen was taken from a ledge 2,300 yards 

 due west of the southern end of the lake on the plateau and 1-5 miles north of 

 the Boundary line. It represents a specially large, relatively homogeneous mass 

 a mile long and 400 yards wide, which crowns the 4,200-foot summit west of 

 the lakelet. This mass is made up of the leucocratic phase of the alkaline body. 

 (Plate 39, B). 



