834 DIAMOND-DEPOSITS OP COPETON, N.S.W., 



Norm of the Oakey Creek quartz-dolerite. 



Quartz 9-36 



Orthoclase 7-21 



Albite 20-96 



Anorthite 24-20 



Hypersthene 20*14 



Calcite 380 



Corundum ... ... ... ... ... 030 



Magnetite ... ... ... ... ... 4-18 



Apatite 031 



Ilmenite 1-52 



Water 7-31 



99 29 



Norm of the Staggy Creek quartz-dolerite. 



Quartz 2-70 



Orthoclase 9-62 



Albite 3301 



Anorthite 2669 



Diopside 14-52 



Magnetite 4-16 



Ilmenite 2-44 



Calcite 230 



Water 4-83 



100-27 



Both the microscopical examination and the analyses of the 

 Oakey Creek and Staggy Creek rocks indicate their close relation- 

 ship. The association of each of them with diamonds in Tertiary 

 river-gravels is another harmonic relation. In view of the 

 evidence for the occurrence of diamonds in the Oakey Creek 

 dolerite, there can be little doubt that the Staggy Creek rock is 

 also diamond-bearing. 



The diamonds in South Africa seem to be found associated 

 with a more basic rock — a peridotite in which the silica-per- 

 centage is often below 40 %, and the percentage of magnesia 

 above 25 %. There cannot, therefore, be said to be a close 

 relationship between the South African peridotites and the 

 Copeton dolerites. 



