REPORT OF THE DIRECTOR AND STATE GEOLOGIST 



r55 



While there is unquestionably some primary hornblende in 

 this rock, much of this mineral is secondary after augite, and most 

 of the rock is not sufficiently fresh to permit a good judgment 

 as to the relative proportions of the two. When The respective 

 amounts of hornblende and augite are compared, much variation 

 is found, and some of the rock would be more properly described 

 as a diorite, rather than a gabbro. In general the augite pre- 

 ponderates, and the close relationship between these rocks and 

 the anorthosites is so evident that the general application of the 

 term, gabbro, to the whole is perfectly justifiable. 



The ilmenite lor titaniferous magnetite) and the zircon are 

 quite as in the anorthosite. Occasional crystals of the latter are 

 of sufficient size to be visible with a hand lens. 



Pyrite and pyrrhotite are not as abundant as in many parts of 

 the anorthosite, but both are sparingly present. 



The great abundance of apatite in much of the rock is one of 

 its unusual features. In addition to the usual minute, slender 

 crystals is much coarser apatite in irregular grains, often con- 

 centrated in little streaks which run clear across a slide. It is 

 very irregularly distributed, but at a rough estimate there is 

 from 3;/ to 5< in the rock as a whole, and several of the slides 

 show from 5;/ to 10^. 



As has been stated, this rock underwent deformation while 

 deeply buried. The individual crystals were strained, bent, 

 broken and more or less completely granulated, with considerable 

 recrystallization accompanying the process. That much of the 

 granular feldspar has been recrystallized is indicated by the fact 

 that much of it does not contain the minute inclusions which are 

 so characteristic a feature of the original feldspar. In part also 

 the granular feldspar is untwinned. and such individuals usually 

 show irregular, patchy intergrowths of two different feldspars. 

 This has not been carefully investigated, but such intergrowths 

 are also found iu some undoubted labradorites, and Becke's 

 method indicates little or no difference in refractive power be- 

 tween the two feldspars. 



