G. 0. Martin — D unite in Western Massachusetts. 245 



to another is gradual and may be traced in the external appear- 

 ance as well as in the mineralogical and structural details. 



The most abundant and generally distributed form of the 

 rock is hard, compact, and moderately fine-grained. In mass 



THE CHESHIRE 

 DUNITE ARE/\, 



the color is light to dark green, even approaching black, but 

 the translucent splinters are light green usually with enough 

 black specks to give the darker appearance. The density is 

 from 2'9 to 3. The rock weathers readily in a well-marked 

 zone to a yellowish brown " muscovado." This rock shows in 

 thin section a badly shattered mass of olivine serpentinized 

 along the cracks. Black opaque grains are scattered through 

 it. The olivine fragments extinguish in groups, each of which 



