272 



PENTTI ESKOLA 



Small amounts of deep green hornblende (/3d = 1.677^0.002) 

 are associated with the pyroxene. 



Considerable quantities of epidote occur near the margins of 

 the skarn inclusions. Its refringence varies within single grains, 

 being lowest in the centers. 



On the hillside just north of Becket Station there is exposed a 

 vertical layer of limestone, surrounded by clinopyroxene gneiss. 







00 

 Heoenbergite 



Fig. 2. — Variation of the indices of refraction in the diopside-hedenbergite series. 

 The small amounts of ferric oxide present have been calculated as ferrous oxide. 

 After E. A. Wiilfing and G. Flink. The indices of pure diopside were determined by 

 H. E. Merwin. 



A specimen of the limestone was found to contain, besides calcite, 

 much quartz arid clinopyroxene of the composition DieyHejj, 

 having /3d = 1.698=1=0.002. 



One of those narrow valleys within the Becket gneiss area that 

 are underlain by the Coles Brook limestone is Goose Pond Brook 

 Valley. It joins the broader East Lee Valley near East Lee. 

 Limestone occurs in small outcrops in the bed of the brook, and 

 little can be said about its mode of occurrence, but it seems to be in 

 immediate contact with the clinopyroxene gneiss that is exposed 

 close by. 



