33 



This rock is well shown in Current River park where a 

 large area of rock was stripped of its covering of recent 

 deposits by a flood caused by the bursting of a dam. Most 

 of the surface rock so exposed is compact diabase, but 

 numerous patches of black Animikie slate, ranging in 

 thickness from a few inches to several feet, are scattered 

 about over the surface. This slate is considerably baked 

 by contact netamorphism, and the sill itself is finer grained 

 near the contact than elsewhere, though at no part does it 

 become very coarse grained. In some places through segre- 



Black Animikie slate; Prospect Street, Port Arthur. 



gation of the phenocrysts of labradorite the rock grades 

 from a typical diabase into masses from two to ten feet 

 (.6 to 3 m.) in diameter having the composition of anortho- 

 site. 



Animikie. — The Animikie or Upper Huronian is 



essentially a sedimentary series and is important as a 



silver and iron-bearing formation. The complete section 



is not well exposed at Port Arthur, but two of the members 



35069—3 



