308 DEPARTMENT OF THE INTERIOR 



2 GEORGE V, A. 1912 



Analysis of augite minette — Continued. 



Mol. 



Na.O 2-39 -039 



K 2 4-80 -051 



' HoO at 110°C : -26 



H 2 above 110°C 1-24 



P 2 0, -66 -005 



100-25 



Sp.gr 2-831 



The calculated norm is : — 



Orthoclase 28-36 



Albite 20-44 



i Anorthite 13-62 



Diopsfile 14-18 



i Olivine 8-47 



Hypersthene 7-48 



Magnetite 3-02 



Ilmenite. 1-67 



Apatite 1-55 



Water 1-50 



100-29 



In the Norm classification the rock enters the sodipotassic subrang, mon- 

 zonose, of the domalkalic rang, monzonas-e, in the dosalane order, germanare. 



Horrjblende-augite Minette. — A somewhat allied type of minette, dis- 

 tinguished, however, by a notable and essential proportion of hornblende among 

 the phenocrysts, occurs as a ten-foot dike outcropping on the -western bank of 

 the Columbia river, a few hundred feet south of the Boundary line. Though 

 occurring just beyond the limit of the Selkirk system this dike may best be 

 described here. Its relations are shown in Figure 23. Huge dike-like masses of 

 an uncrushed, fresh biotite-hornblende granite porphyry cut the intensely 

 crumpled Pend D'Oreille phyllites and one of the porphyry masses is itself cut by 

 the dike in question, which is ten feet wide and strikes N. 10° E. with a dip of 

 about 75° to the eastward. It truncates a seven-inch dike of augite minette 

 cutting the phyllite, as shown in the figure. 



The dike of hornblende-augite minette shows a very marked chilling along 

 both walls. Its main mass is composed of a dark greenish-gray to dark ash- 

 gray, fine-grained rock, macroscopically showing occasional phenocrystic foils of 

 biotite up to 2 mm. in diameter and many minute prisms of augite and green 

 hornblende varying from 0-5 mm. or less to 1 mm. in length. These three 

 femic minerals are embedded in a very fine-grained paste of doubtless sodiferous 

 orthoclase and oligoclase (in about equal proportions) accompanied by abundant 

 titanite, apatite, interstitial quartz, and a small amount of ilmenite as the acces- 

 sories. The rock is somewhat weathered, with calcite, quartz, kaolin, chlorite, 

 and epidote as the secondary products. The hornblende and augite are present 

 in nearly equal amounts and each rivals the biotite in abundance. The specific 

 gravity of this phase is 2-740. 



