Plate 15 



A. Uncrushed anorthosite showing the twinning of the 

 labradorite. The original rock was almost black in color 

 and was obtained at the southwest border of the quad- 

 rangle, west of the Boreas ponds. Crossed nicols, actual 

 field 0.1 inch or 2.5 mm. 



B. Part of a large augite crystal in the anorthosite, 

 figure in A, above. White light, actual field o.i inch or 

 2.5 mm. 



