650 DIALLAGE ROCK. 



in the mixed rock than to occur in distinct masses 

 or strata. 



SECOND DIVISION. 



Compound : of two ingredients. 



A. A mixture of diallage and felspar. 



a. With platy felspar. 



b. With fine granular felspar. 



c. With compact felspar. 



The aspects of these mixtures vary much, 

 both according to the proportions of the con- 

 stituent minerals and to the magnitude of the 

 parts. These are sometimes so minute that the 

 peculiar character of the diallage disappears. 



B. Diallage and actinolite. 



C. Diallage and talc, or chlorite. 



D. Diallage and serpentine. 



The varieties B, C, are rare. D is also, for 

 convenience, enumerated under the head of Ser- 

 pentine ; since it is often difficult to determine 

 whether this variety, occurring at the common 

 boundary of diallage rock and serpentine, belongs 

 to the former or the latter. In general, in some 

 parts of this transition, the diallage abounds so 

 as nearly to exclude the serpentine. 



