S ON HAUYNE-TRACHYTE AND ALLIED ROCKS. 



The minerals whicli we have detected in these rocks 



Alkali Syenite (Augite Syenite). 



Sp.gr. 2-6. 



Found 1)1 situ on beach south of Regatta G-round, Port Cygnet, 

 massive exposure, but lying at the water-level. 



No 



M acroscop ic characters . 



Medium grain ; brownish grey, syenitic looking ; has 

 an elaeolitic appearance, with greasy feel. With porphy- 

 ritic tendency by reason of a few large glistening felspars 

 (nearly y long) scattered sparingly. Nq rhomb-shaped 

 sections of felspars seen. Numerous small brilliant dark 

 garnets appear as specks, Avhich can be well recognised 

 with the pocket-lens ; many of these seem enclosed in the 

 felspars. The rock resists decay well, as shown by the 

 thinness of the weathered crust, decomposition not extend- 

 ing far into the interior of the stone. 



Microscop ic cliaracters. 



Structure, normal hypidiomorphic-granular (granitic), 

 with an occasional leaning to the trachj^tic type by an 



