COMPOSITION OF CANCRINITE. 241 



the eleolites and the larger albites. Dr. Clarke,* arguing from the result 

 of his analysis of the mineral, declares that most of the cancrinite of the 

 Litchfield rock is an alteration product of eleolite ; while Rosenbusch,f 

 on the other hand, cites it as an especially fine example of primary can- 

 crinite. The microscope shows conclusively that some of the cancrinite 

 has resulted from the alteration of eleolite. The most of it, however, is 

 so far removed from eleolite that its relation to this mineral has not been 

 discovered. It occurs principally in the mosaic, which has been thought 

 to be of secondary origin, and is the youngest of its constituents, with 

 the exception of socialite. It has certainly crystallized from the magma 

 that yielded the other minerals of the mosaic, and in this sense is orig- 

 inal, but its chemical components may nevertheless have come from 

 some of the eleolite that was destroyed at the time of the formation of 

 the mosaic. 



The composition of the commonest type of the cancrinite, the bright 

 yellow granular variety, is as follows : 



Discussion and Summary. — A noticeable fact in connection with this 

 rock is the absence of sphene, hornblende and augite. The former is 

 present in nearly all normal eleolite-syenites, with the exception of those 

 from Kangerdluarsuk in Greenland and from Funfkirchen in Hungary ,| 

 while one of the last two is usually found, even though biotite be the 

 most prominent of the bisilicates present. Another fact of interest in 

 connection with the Maine rock is the great preponderance of albite 

 among the feldspars. An analysis of the most common phase of the 

 rock by Mr. L. G. Eakins gave: 



Total 99.95 



Jour. Sci., 3d ser., vol. xxxi, 18S0, p. 203. 

 t Mil i lie Physiographic, ii. 1887, p. 81 . 



[bid . p 



