328 DEPARTMENT OF THE INTERIOR 



2 GEORGE V, A. 1912 



Augite-olivirve Latite. — This type has been identified at only two localities- 

 in the Boundary belt. On Record mountain ridge it is interbedded with the 

 chemically analyzed biotite-augite latite; it also occurs on the top of the broad 

 ridge west of Malde ridge at a point about a mile and a half north of the 

 Boundary line. The specimens collected at these places are comparatively- 

 fresh and are uncrushed. 



Macroscopically, there is little to distinguish these rocks from the more- 

 common angite latite. The colour, grain, and general habit is the same. The 

 phenocrysts are augite, olivine, and labradorite (averaging Ab, An.,). The 

 ground-mass may be cryptocrystalline, devitrified-glassy, or microcrystalline, 

 with greater or less development of microlitic augite and labradorite. The 

 accessories and secondary products are the same as those in the angite latite, 

 except that a little phenocrystic biotite is developed in the specimen from; 

 Record mountain ridge. 



That specimen (No. 465) has been analyzed by Mr. Connor. The micro- 

 scope showed that the augite is here somewhat uralitized and the olivine partly 

 serpentinized, while the plagioclase is very fresh. The hyalopilitic base bears 

 microlites of labradorite, magnetite, apatite, and possibly orthoclase;' most of 

 the ground-mass is, however, a glass which is turbid through the very abundant 

 generation of sericitic mica and other secondary products. The specific gravity 

 of three specimens from this locality varies from 2i-70O to 2-751; the higher- 

 value is the more reliable since it refers to the freshest specimen. 



From the chemical analysis it is clear that this latite verges on augite 

 andesite. 



Analysis of [ augite-olivine l-atite. 



Mol. 



SiO, 58-67 -978 



TiO- 1-00 -013 



A1 2 3 15-67 -154 



Fe,A 2-85 -018 



FeO. 3-28 -046 



MnO -11 -001 



MgO \. 3-86 -097 



CaO 5-33 -095 



SrO -09 -001 



BaO -11 -001 



Nzu.0 4-77 -077 



K 2 308 -033 



HjO at 110°C -02 



H e O above 110°C -54 



P 2 B -16 -001 



99-54 



Sp.gr 2-751 



In the Norm classification the rock enters the dosodic subrang, akerose r 

 of the domalkalic rang, monzonase, in the dosalane order, germanare. -The 

 norm is as follows: — 



