90 



Nepheline 63-18 



Oligoclase 29-66 



Muscovite 4*39 



Calcite 1-42 



Corundum -50 



Biotite -50 



Magnetite • 10 



2. Congressite. — This rock represents the product 

 of differentiation in which nepheline is most abundant. 

 It is allied to monmouthite and urtite but is richer in al- 

 kalies belonging to the 9th. order of the persalanes in the 

 quantitative classification. The rock appears as great 

 exposures in that part of the Craigmont hill known as 

 Congress Bluff. It is rather coarse in grain and usually 

 possesses a more or less well marked foliation, as in the 

 case of the other members of the series. It is pale pink in 

 colour owing to the large amount of nepheline which it con- 

 tains this mineral having a pink colour and a distinct oily 

 lustre. In places, however, the rock displays little white 

 bends or streaks of albite. Sodalite when present occurs 

 enclosed in the nepheline in the form of small grains which 

 are bright blue in colour, while the other constituents 

 occur as little flakes or grains, distributed through the rock 

 serving to mark the foliation. The mica in some cases 

 displays a tendency to segregate into little bunches. 

 An analysis of the rock is given on page 96 . 

 The following is the "mode" or actual mineralogical 

 composition of the rock as calculated from the analysis : — 



Nepheline 72 



Orthoclase 



Albite 



Sodalite 



Muscovite 



Biotite 



Apatite 



Magnetite 



Ilmenite 



Pyrite 



Calcite 



Water 



99-80 



No orthoclase could be found in either Craigmontite 

 or Raglanite when separations were made by Thoulet 

 solution. No separation has as yet been made of the con- 

 stituents of Congressite to confirm the presence of the 

 small percentage of orthoclase indicated by analysis. 



72 



4 



46 

 •14 



3 



•67 



2 



•22 



6 



•55 



3 



•36 





•34 



3 



•7i 





•46 





•36 



1 



•80 





•7i 



