Rocks of Noyang. 31 



These measurements suggest albite, but are not incompa- 

 tible with oligoclase ; and the discussion of the analysis of 

 this rock causes me to favour the latter view. 



A slice from a rock collected on the upper part of the 

 Mount Elizabeth branch gave me favourable sections for 

 optical measurements of the felspars, and I found these to 

 be in the zone OP — ooPoo between 2° 30' and 16° 45'. 

 This, again, agrees rather with oligoclase than albite. 



Quartz fills in the spaces left vacant by the previously 

 described minerals. It usually is composed of several 

 crystalline granules, and otherwise completely resembles the 

 quartz in other crystalline-granular rocks of a granitic cha- 

 racter. I observed as inclusions — (1) Magnetite crystals, 

 (2) laminae of mica, (3) felspar fragments, and (4) small 

 colourless crystals, apparently monoclinic. 



Sphene. This mineral occurs, but not so frequently as 

 might have been expected. The examples which I have 

 observed have been rough crystalline grains; and in only 

 one instance did I observe a well-formed crystal of the 

 characteristic double wedge-shaped form. 



Apatite occurs in the usual small and somewhat lengthy 

 prisms. 



I carried out a quantitative analysis of a portion of the 

 same rock from which the thin slices were prepared : — 



No. 3. QuARTZ-MlCA-DlORITES. 



Katio. 



19-23 ... 4-1 



4-64 ... 1- 



4-69 ... 1- 



2-52 ... -5 







Per cent. 



Molecular 

 Proportions. 



p 2 o 5 



... 



•22 



... -03) 



Ti0 2 



... 



•03 



... -01 V = Si0 2 



Si0 2 



... 



57-69 



... 19-23) 



A1.0, 





15-65 



7-42 



... 3-04) p n 



FeO 





2-41 



... -67^ 



MnO 

 CaO 





tr. 

 6-92 



::: »£ r R0 



MgO 





3-10 



... 1-55J 



K 2 



... 



2-37 



•50) 



N£ 2 



. .-» 



2-33 



... •75l=K 2 



n,b 



... 



1-59 



... 1-77 j 







99-73 



30-95 



Hygroscopic 



moisture 



•34 



Specific 



gravity 



... 2-779 



