850 



NEW YORK sa?ATE MUSEUM 



in some of the rocks and the latter predominating in others. The 

 olivin diabases are in general less feldspathic than those in 

 which that mineral is lacking. Much variation in structure is 

 also shown which, to a considerable degree at least, depends on 

 composition. The ophitic structure is the more usual one. In 

 many of the dikes, however, the interspaces between the feldspar 

 laths are filled by clumps of smaller augites, instead of the large 

 augites which solidly fill the interspaces in the typical structure. 

 In the more feldspathic dikes the interference of the different 

 feldspar laths with one another, and their abundance much 

 hinder the development of the normal structure. 



In many of the dikes there is a more or less well marked 

 tendency on the part of the feldspar laths to assume a radial 

 grouping around various centers, giving rise to the divergent 

 rayed structure. In some such the augites also tend to a long 

 prismatic, or lath, shape, and these may take on an independent 

 radial grouping also. A tendency on the part of the augites to 

 show their own crystal boundaries is found in many of these 

 rocks, as Kemp has shown, producing a grading toward 

 camptonite. 



Chemical analyses and discussion 



5 

 50.89 

 15.39 



5.77 



52.53 

 18.31 

 .34 



7 



63.02 



14.87 



6.53 



6 . 43 none 



67.16 

 14.53 



4.17 



68.96 



15.25 



3.28 



7.6 



1.82 



.95 



.41 





2 



8.75 



3.15 



1.12 



1.26 





76 



5.67 



7.26 



5.85 



5.55 



5 



45 



2,72 



6.47 



5.62 



6.1 



5 



01 



2.46 



1.16 



1.59 

 .4 

 .32 



1.45 



1.1 





91 





.15 



.46 







23 



Total .. 100.54 98.75 99.66 100.2 99.25 99.93 99.87 100.28 100.05 

 0=C1 & F 14 .22 



100.06 



99.71 



