GEOLOGY AND PETROGRAPHY OF THE PROSPECT INTRUSION. 479 



The maximum percentage of ilmenite is found in certain 

 bands near the upper aplitic vein. 



Specimen H was obtained beneath the aplitic vein, where 

 it thickens near the middle of the quarry face (see fig. 4). 

 It is similar in most respects to specimen C, but biotite is 

 very rare. Apatite, on the other hand, is much more 

 abundant — a feature which seems to be a general rule in 

 the vicinity of the aplitic veins. The rock is rather 

 decomposed and contains a good deal of analcite, which 

 appears to be all secondary after plagioclase. 



Specimen I (J and K idem.) 

 Locality. A little below the lower aplitic vein a few metres 

 to the left of where this begins to rise. The specimen is 

 typical of the greater portion of the rock underlying the 

 aplitic vein in this quarry, and came from about 18 m. (60 

 feet) below the junction. 



Megascopic Description. Colour grey. Grainsize fairly 

 coarse. Minerals : augite, plagioclase, ilmenite and analcite, 

 are easily recognised with a pocket lens. The rock is fairly 

 fresh — the least decomposed sample of the coarse rock 

 which has been found. 



Microscopic Description. Texture : Crystallinity, holo- 

 crystalline ; grainsize average 1 to 5 mm.; fabric, hypidio- 

 morphic-granular, approaching pilotaxitic. 



Minerals Present. 





I. 



II. 



III. 



Calculated from 

 analysis. 



Calculated. 



Measured and 



corrected. 



Augite 



38*2 



Augite 38*2 



40*5 



Plagioclase 



35*7 



Felspars 38*0 



37*2 



Orthoclase 



2*3 



Iron Ores 16*0 



16*6 



Ilmenite 



8*4 



Olivine 5*7 



4*9 



Magnetite 



7*6 



Biotite 1'7 



0*1 



Olivine 



5*7 



Apatite 0*4 



0*7 



Biotite 



1-7 









Apatite 



0-4 



100*0 



100*0 



lOO'O 



