58 



Rocks of Noyang. 



A large part of the rock is made up of minute quartz 

 grains. In addition to these constituents there is hydrated 

 iron ore, and much black granular material, which is not 

 affected by long digestion in hydrochloric acid, but is 

 removed by ignition of the slice, and which, therefore, is 

 carbon. 



The following analysis is of part of this sample, and the 

 calculation of the percentages has been based upon the 

 microscopic examination : — 



No. 8. — Slates. 









Per cent. 



Molecular 

 Proportions. 



Ratio. 





p *o 5 







•23 



•03 







Si0 3 







.. 62-30 



.. 20*71 



Si0 2 = 



20-71 



A1.0, 







.. 19-22 

 1-80 

 4-01 



3-73 ) 



•22 j 

 1-11) 



R 2 ° 3 = 



3-95 



CaO 



MgO 







•44 

 2-95 



.. -16 I 



1-48) 



EO 



2-75 



K 2 







3-60 



•77 ) 







Na 2 







2-07 



•67 V 



R 2 = 



3-06 



n.b 







2-36 

 98-98 



2-62 j 

 31-50 







Hygroscopic 



moi 



sture, -40 









Specific 



gravity 



... 2-727 









