138 



G. D. OSBORNE. 



(g) Pyroxenites — No rocks of this type were found by the 

 author but the following is an analysis by Mr. Mingaye 1 

 of a diallage rock from the Basin : — 



Si0 2 



... 50-36 



Ti0 2 



trace 



A1 2 3 



2-46 



C0 3 ... 



4-41 



Fe 2 3 



4-26 



Cr 2 3 



•04 



FeO... 



4-41 



NiCoO 



•31 



MgO 



20-76 



MnO 



•29 



CaO... 



6-25 



BaO... 



•02 



Na 3 



•51 







K 2 0... 



•09 





100-45 



H 0- 



2-21 

 4-07 







xj. 2 w 



H 2 + 







(h) Other rock Ujpes within the Basalt. — Under this 

 heading it is desired to mention briefly the nature of three 

 sections of rock material, which contain some most unusual 

 characteristics in their mineral content. Two sections 

 were cut from a small inclusion which was associated with 

 gabbro and Iherzolite in a closely packed portion of the 

 dyke. Under the microscope both sections show very 

 similar features. Fortunately in one slide the junction of 

 the iuclusion and its host, the basalt, is presented. The 

 rock consists essentially of two minerals quartz and another 

 colourless mineral, whose characters, if not anomalous, 

 suggest something fairly rare as a rock constituent. The 

 structure isallotriomorphic granular and the second mineral 

 has included the quartz. However, the quartz does not 

 appear to be normal. The appearance is rather that of 

 recrystallised quartz in most cases, yet its inclusion in the 

 second mineral appears more or less ordinary. 



The second mineral shows a fine felted or fibrous appear- 

 ance similar to many secondary silicates after olivine. 

 Against these fibres the extinction is practically parallels 



1 Ann. Rept. Mines Dept. N.S.W., 1908, p. 174. 



