South African (iRA.xiTES. 



28c: 



All these orthite-hearing rocks have a distinctly gneissic aspect 

 which is sufficient to suggest a secondary or metamorphic origin for 

 the orthite even apart from its association with epidote. The 

 presence of irarnet appears to point in the same dire<^- 

 tion. The fact of the epidote being idiomori>hic 



towards the mica points, however, to its primary nature, 

 and it niav lie remarked that the Northern Rhodesian rock> 



BIDTITE ENCLOSING EI'lUOTE WHICH SIKKOCNDS UKTHrrE. 



contain micropegmatite. a fact which appears ahsolutelv con- 

 clusive as to their igneous origin. It may also be mentioned that fine- 

 grained modifications of the Jibuyi rock contain correspondinglv 

 small cr)stals of orthite, and we seem accordingly driven to regard 

 both orthite and epidote as normal products of the consolidation of a 

 molten magna. 



