The Petrography of the Granitic Hocks, 



■9 



The mica-gabbi-o yielded at the rate of 1 3 grains of gold and 6 grains 

 of silver per ton. 



THE MINERALOaiCAL COMPOSITIONS AND CLASSIFICATION. 



The essential original minerals which are present in these rocks are 

 as follows : — 



Quartz, orthoclase, microcline, oligoclase, albite, muscovite, biotite, 

 augite, hornblende, titaniferous iron-ore, magnetite, sphene, apatite, 

 zircon, and, in one case only, glass. From the results of the chemical and 

 microscopical examinations outlined in the preceding pages, the minera- 

 logical compositions of the rocks have l^een calculated as follows : — 



