498 H. S. JEVONS, H. I. JENSEN, T. G. TAYLOR AND C. A. SUSSMILCH. 



olive-green and deep bluish-green. Its D.R. is approxi- 

 mately 0*020. Both chlorite and chloritoid occur replacing 

 augite, the former more abundantly, and also filling veins 

 and small pockets in the decomposing felspars. The form- 

 ation of these minerals does not take place until the augite 

 decomposes, which does not begin until the olivines have 

 completely gone and the felspars have been very largely 

 altered. 



Cavities in the rock and opened joint cracks often con- 

 tain masses of a homogeneous dark green chloritic material. 

 It is amorphous to the naked eye, and a broken surface has 

 something of a waxy lustre. Mr. J. W. Hogarth very 

 kindly analysed one of these masses for us at the Sydney 

 Technical College, with the result stated in column I. of 

 the following table : — 





I. 



II. 



III. 



Si0 2 



14*9 



30*5 



33*5 



A1 2 3 



4'7 



10-0 



11*0 



Pe 2 3 



6-1 



12*5 



14*0 



MgO 



106 



22*0 



24'2 



CaO 



29'7 



2*0 



2'2 



K 2 



0*3 



0*5 



0*6 



H 2 at 100 c 



ll'O 



22-5 



14-5 



C0 2 



22*6 



... 



... 



MnO 



trace 



... 



... 



99'9 lOO'O lOO'O 



The analysis is only an approximate one which was^ 

 carried out solely for the purpose of gaining a rough idea 

 of the composition of this mineral. There is obviously 

 much calcite in it, and if to the 22*6 per cent, of C0 2 we 

 allot 28*7 parts of CaO we find that about 51 per cent, of 

 the chloritic mass is calcite. Subtracting this we find the 

 remainder has the percentage composition shown in Column 

 II. This is too high in water for any of the chloritic or 



