241 



specimen it is a fine-grained rock, apparently chiefly com- 

 posed of amphibole with a little felspar. . Microscopically 

 it is seen to be a uralitic-diabase. The texture is diabasic, 

 approaching the charactei^stic ophitic structure. Actinolitic 

 uralite is the predominant mineral. It is dark-green and 

 strongly pleochroic. It is slightly dusted with secondary 

 magnetite. Brown plagioclase (labradorite) occurs in idio- 

 morphic laths, and sometimes is slightly zoned. Angiilarly- 

 bounded irregular grains of magnetite are abundant. Quartz 

 occurs intersertally. Fine-grained epidote is abundantly 

 scattered all through the rock. 



This rock is another instance of the epi-diabases so com- 

 mon in southern South Australia, to which reference has 

 been made above. 



The Geological Department, 



University of Sydney. 



