REPORT OF THE CHIEF ASTRONOMER 



357 



SESSIONAL PAPER No. 25a 



The olivine of the ground-mass (up to 3 mm. in diameter) is abundant and 

 very fresh; it has a bottle-green colour in the hand-specimen and is colourless 

 in thin section. It is sometimes slightly serpentinized along cracks. The augite 

 is a diopside, occurring in stout prisms up to 2 mm. in length. The plagioclase 

 is labradorite between Ab 2 An„ and Ab 3 An 4 . Orthoclase is plentiful and, like 

 the labradorite, is extremely fresh. The feldspars are much smaller than the 

 olivine or augite, the plagioclase averaging about 0-2 mm. in diameter, the 

 orthoclase about 0-4 mm. Titaniferous magnetite and apatite are fairly 

 abundant accessories. The order of crystallization appears to be : 1. The acces- 

 sories. 2. Olivine. 3. Augite. 4. Biotite of ground-mass and biotite phenocrysts. 

 5. Labradorite. 6. Orthoclase. 



The rock of the Fifteen-mile creek mass is, in all essentials, like the one just 

 described, but its facetting is even more pronounced. The mica phenocrysts 

 range from 2 cm. to 5 cm. in diameter by 0-5 mm. to 1 mm. only, in thickness. 

 Curiously enough, the grain of the ground-mass is, in the specimens collected, 

 inversely proportional to the size of the mica phenocrysts. In the Fifteen-mile 

 creek body the phenocrysts are about double the size of those in the Christina 

 lake rock, while the diameters of the respective ground-mass feldspars average 

 about as one to two. That is, these feldspars in the rock with the larger mica 

 phenocrysts have an average volume only about one-eighth of the average volume 

 of the feldspars in the rock with the smaller phenocrysts. 



The average specific gravity of two specimens from Christina lake is 2 ■ 841 ; 

 the average for two specimens collected at the eastern locality is 2-815. 



^Ir. Connor has analyzed a specimen (No. 354) from the Christina lake 

 body, with the following result (Col. 1, Table XXIV.) :— 



Table XXIV. — Comparison of basic syenite and average m-iniette of region. 



1. 



Si0 2 52-95 



TiO, -70 



Al 2 d 3 14-00 



Fe 2 3 2-57 



FeO 5-55 



MnO -13 



MgO 7-29 



CaO 6-93 



SrO -11 



BaO -32 



Na 2 2^73 



K 2 , 509 



H„0 at 110°C - -16 



H 2 stove 110 C C -50 



C0 2 



P 2 5 47 



99-50 



Sp.gr 2-872 





La. 



2. 



•882 



51-78 





009 



•87 





137 



14-54 





016 



1-77 





077 



5-29 





002 



•11 





182 



6-89 





123 



7-35 





•001 



•07 





002 



•25 





044 



2-74 





054 



4-60 



•44 



1-91 



•88 





•004 



•83 



100-32 



