Na,0 



3-85 



Ilmenite 



K 2 



2-30 



Apatite 



H 2 0- 



1-76 



co 3 



H„0 + 



2-36 



Water 



co, 



•71 





TiO„ 



•41 





P.O. 







NiCoO 



03 





MnO 



•20 



Classification 



The analysis supports the determination of the plagioehiM- 

 as labradorite. A further point of interest is that though 

 the rock is evidently fairly rich in the olivine molecule, 

 plagioclase has been the first mineral to crystallise. The 

 rock may be found in all stages of carbonation, the final 

 condition being a yellow-grey rock taken in hand specimen 

 to be a felspathic sandstone. Sections however show the 

 parallel arrangement of the felspars, and that these are 

 scarcely attacked while the glass has been completely 

 decomposed. 



Part III. Mineralogical Notes. 



In the vughs in the breccia and basalt of Dundas one 

 may find well crystallised quartz and amethyst; carbonates 

 in the form of calcite (of Iceland spar and nail-head types), 

 and small flat rhombohedra of brown siderite are not un- 

 common. In the cracks of the basalt slender prisms of 

 (tvuifnnite occur. They maybe over a centimetre in length 

 and perhaps a couple of millimetres thick. Usually they 

 are twinned. A small crystal was found untwinned and 

 its angles were measured by Mr. L. L. Waterhouse, b.e. 

 His figures proved the crystals to be aragonite, and deter- 

 mined the presence of the following forms (010), (001), (110), 

 (011), (012), (013). From his figures and sketches the clino- 



