REPORT OF THE CHIEF ASTRONOMER 283 



SESSIONAL PAPER No. 25a 



occurring in this part of the Selkirks. The isolated peridotitic sill, hornblendite, 

 may be of the same general date as the schistose derivatives of the gabbro or may 

 be younger. 



Abnormal Granite Intrusive into the Kitchener Quartzite. 



At the edge of the Kootenay river alluvial flat and 2,000 yards south of 

 Corn creek, the down-faulted Kitchener quartzite is cut by a peculiar granular 

 rock exposed in the form of a band about 600 feet wide and elongated in the 

 strike of the invaded quartzite. The igneous mass seems to be in sill-relation 

 to the sedimentaries, although the exposures are not sufficient to cause certainty 

 on that point. The dip of the adjacent Quartzite is 60° to the southeastward; 

 if the intrusive body is a sill its thickness is nearly 500 feet. 



The igneous rock is dark bluish-gray, medium-grained, and has the habit 

 of a quartz diorite. In the hand-specimen idiomorphic, lustrous black prisms 

 of hornblende up to 5 mm. in length are very abundant; these are often arranged 

 with a rough fluidal alignment. Quax'tz is easily recognized as a dominant 

 constituent; feldspar is as clearly subordinate. 



Under the microscope the rock is seen to be very fresh, though slightly 

 strained, with possibly some granulation in places. The observed amount of 

 deformation is not sufficient to explain the rough parallelism of the hornblende 

 prisms, which is apparently a primary feature established during the crystal- 

 lization of the magma. The essential and accessory constituents are here 

 listed in their order of quantitative importance (by weight) as determined by 

 the Rosiwal method : — 



Quartz 41-3 



Hornblende 33-4 



Orthoclaee 19-2 



Garnet 2-8 



Magnetite 2-1 



Epidote -6 



Apatite -5 



Zircon -1 



100-0 



The hornblende is highly pleochroic, with unusually beautiful tints : — 



a — Light yellowish green. 



b — Very deep olive green. 



C — Bottle green with pronounced bluish tinge. 



Absorption very strong: b>C>a. 



The extinction on (010) is about 11° 15'; that on (110), about 13°, as 

 average of eight measurements on cleavage pieces. Etch-figures on (110) show 

 that c lies in the obtuse angle /? in Tschermak's orientation of amphibole, and 

 also that the hornblende is rich in alumina. The hornblende is quite idiomor- 

 phic in the prismatic zone but the prisms are seldom, if ever, terminated by 

 crystal faces. They lie in a mesostasis of quartz and feldspar and have suffered 



