REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1900 I'SS 



When the apparent gabbro from the middle of the cut is more 

 carefully examined, it is seen to be quite peculiar. It holds some 

 30fc of non-feldspathic minerals, zircon, titanite, apatite, pyrite, 

 magnetite, garnet, augite, biotite, hvpersthene and hornblende 

 and at least ^fc of quartz. So far as can be told from the pres- 

 ence or absence of twinning there is barely a scrap of plagioclase 

 in the rock, the feldspar consisting of irregular intergrowths of 

 two different feldspar species, probably orthoclase and an acid 

 plagioclase. Two little cores of plagioclase within these feld- 

 spars give the impression that all is secondary and due to the 

 alteration of a plagioclase. This rock will be reverted to later 

 when a similar rock from another locality is under discussion. 

 As it stands, it has more affinities with the augite syenites than 

 with the anorthosite. Its boundaries are not well exposed, sc^ 

 that it is not certain that it is a dike, though this is most 

 probable. 



In the third cut, IJ miles from Saranac depot, there is also 

 shown an association of granular anorthosite gabbro (976) run- 

 ning into coarse phases. Here also is a crushed and altered strip 

 of white and decayed looking rock, which proves firm and merely 

 altered, not decayed. The feldspar has gone to saussurite, an 

 alteration product consisting largely of zoisite. Considerable 

 epidote has developed locally, likely from the original augite. In 

 much of this rock the alteration is only partial, feldspar cores 

 remaining. In these^ extinctions up to 22° from the albite 

 twinning plane indicate labradorite as the feldspar. 



At the fourth cut, nearly 2 miles from the depot, the rock i» 

 mostly of the granular anorthosite gabbro type, few labradorite 

 augen remaining (977). The cut is not extensive. 



The fifth cut commences a little over 2^ miles from the depot 

 and is 65 yards long. Here the rock (978) is excessively jointed 

 and sheared, furnishing easy passage for underground waters, 

 and alteration is on a much greater scale than usual. The finer 

 grained portion is w^holly altered, but unchanged cores remain in 

 the large labradorites. These show^ the attack to have been 

 along the outer boundaries and the cleavage cracks of the feld- 



