GEOLOGY AND PETKOGRAPHY OF THE PROSPECT INTRUSION, 535 



and black. Grainsize : Coarse, varies in different specimens 

 from 2 mm. to 10 mm., and occasionally more. Commonest 

 grainsize 2*5 to 3 mm. (denoted fine-grained, limits 2 to 

 5 mm) and 5 to 10 mm. (coarse-grained, limits 5 to 10 mm.). 

 Minerals visible : Felspars, white or chloritic green. Long 

 rectangular crystals are often seen beautifully zoned, the 

 centre clear and glassy, and thus appearing rather dark, 

 the outer zone opaque white owing to kaolinisation. The 

 boundary between the zones is sharp, and is marked in a 

 few crystals by a thin dark line of chlorite, which makes 

 a perfect rectangle. Black prisms of augite are common, 

 and needles of apatite may be seen with a lens. There are 

 also abundant white patches of analcite, and dark green 

 masses of chlorite. 



Microscopic Description. Texture : Holocrystalline, 

 hypidiomorphic-granular. Grainsize, see above. 



Minerals present : — 



Corrected. 



As measured 



Original — Labradorite 50 



49*0 



Albite 33£ 



31-4 



Pyroxene (augite, diopside 





and segyrine-augite) 11 



8*2 



Ilmenite ... ... ... 5 



5-1 



Apatite 0J 



0*5 



Secondary — Analcite 



3*8 



Chloritoid and chlorite 



2*0 



100-0 100*0 



The measurement was made by about 350 separate 

 lengths on each of two slides. In the correction the anal- 

 cite has been divided nearly equally between the albite 

 and labradorite because there is much difficulty in deciding 

 what it replaces when it occurs in patches, and a small 

 allowance has been made for the tendency to overestimate 

 the colored constituents. The measurement should only 



