394 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



• 



compact, and. of a greenish-black colour, mottled with abundant areas of 

 rather pale green talc. Olivine is the only visible primary essential and occurs 

 with its usual granular habit. Neither chromite nor picotite could be certainly 

 detected in any of three sections cut from the hand-specimens from this 

 locality. The analysis shows, however, the presence of a small amount of 

 chromic oxide. The secondary products are the usual ones, serpentine, talc, 

 tremolite, magnetite, and a carbonate which is probably dolomite. Small grains 

 of pyrite, doubtless introduced during the alteration of the rock, were also seen 

 in the hand-specimen. 



Professor Dittrich's analysis of this typical, though partially hydrated and 

 otherwise altered, dunite (specimen No. 282) gave the following result: — 



Analysis of Boclc Creek dunite. 



Si0 2 40-25 



Ti0 2 tr. 



A1 2 3 MO 



Fe 2 O s 4-61 



Cr 2 O a -15 



FeO 3-04 



MnO -11 



MgO 37-91 



CaO 1-16 



Na 2 -48 



K 2 -16 



H„0 at 110°C -32 



H 2 above 110°C 9-08 



C0 2 1-9* 



100-32 

 Sp.gr 2-868 



The hydration of this rock is evidently so pronounced that a calculation of 

 the proper norm is not directly possible. The place of the rock in the Norm 

 classification cannot, therefore, be stated. 



Kettle River Formation. 



General Description. — The map illustrates the fact that the Kettle River 

 formation in its present distribution within the Boundary belt occurs 

 only in shreds and patches. It has been cut to pieces by faults and by dikes, 

 sills, and chonoliths of the various porphyries; it has been deeply buried 

 beneath the Midway lavas. Extensive erosion has in many places uncovered 

 the sediments but has also largely destroyed their continuity by penetrating 

 the entire formation and laying bare much of its Paleozoic floor. In conse- 

 quence of all these events the Kettle River beds now form detached, slab-like 

 masses seldom more than a few hundred yards in width. At least seventeen 

 isolated patches of the formation have been found between Midway and the 

 forks of Rock creek, a distance of fifteen miles in an air line. The formation 

 does not crop out farther west, but small patches of it are probably represented 

 in the northern part of the area mapped by Mr. Brock as the ' Boundary Creek 

 District.' 



