BY H. I. JENSEN. 609 



As shown in Plate xxxi., tig.5, this rock contains aggregates 

 of coarse crystals of olivine, felspar, and pyroxene, not unlike 

 inclusions of partly resorbed olivine gabbro. From this char- 

 acteristic, considered in conjunction with the occurrence of the 

 felspar of talc and muscovite (sericite ?) and of Schiller structure, 

 and with the presence of diallagic augite and an alkaline base, 

 the rock appears to have been formed by the crushing and partial 

 refusion of an olivine gabbro, and the blending of the mass thus 

 formed with an alkaline magma. 



5. Name : Pilotaxitic Orthoclase (and Sodalite 1) Basalt, allied 

 to Trachydolerite. Magmaticname, Akerose (see Tables i. &u.}. 



W.201. Loc: Mt. Exmouth, summit. 



1. Handspecimen a dark bluish-black porphyritic rock with 

 greasy lustre and splintery fracture. 



2. Texture : almost holocrystalline, with very variable grain-size* 

 The base is very tine-grained (microcrystalline) and has a hyalo- 

 pilitic fabric in places, trachytic in others. 



3. Constituents (in order of decreasing amount): felspar occurs 

 in idiomorphic, only slightly corroded phenocrysts of medium 

 labradorite, and in tine microscopic needles varying from albite 

 to labradorite. Olivine in corroded phenocrysts. Augite rarely 

 as very corroded, rounded phenocrysts, but abundant in minute 

 grains throuj^hout the base; it is a titaniferous variety. Magnet- 

 ite in idiomoiphic grains. A little glass is also present, as well as 

 accessories comprising serpentine (decomposition-product), apatite 

 and sodalite (or allied isotro[)ic mineral). 



4. Name : Porphyritic Hyalopilitic Olivine Basalt. 



W.85. Loc: Uargon Tableland, south of Black Mountain. 

 (Plate xxxii., fig.l). 



1. Handspecimen like the preceding. 



2. Texture like W.67 with pilotaxitic-ophitic fabric. 



3. Composition: the phenocrysts comprise felspar varying from 

 acid labradorite to andesine; corroded olivine; augite so inter- 



