Rocks of Noyang. 53- 



This rock was most probably, in its unaltered state, a diorite 

 standing near to the hornblende porphyrites. 



No. 7. — Diorite. 



Molecular Eatio> 



Proportions. 



.. -20) 



.. -34 VSiO-o, &c. = 26-42 ... 7' 



.. 25-88 ) 



" 8 '5* ]>R 2 2 - 3-79 ... 1- 

 •4o f z 3 





Per cent. 



PoO, 



... tr 



co 2 



... -44 



Ti0 2 



... 1-39 



SiO, 



... 47-63 



A1 2 3 



... 17-20 



Fe 2 o 3 



... 3-60 



FeO 



... 8-09 



MnO 



tr 



CaO 



... 6-42 



MgO 



... 6-25 



K 2 



... 1-31 



Na 2 



... 4-65 



H 2 



... 2-71 



2-25^ 

 2-30 ( 



3-12 ; 



EO = 7-67 



•28 

 1-50 VR P 4-79 ... 1-3 



3-01 



99-69 32-13 



Hygroscopic moisture, -73 c 212° F. 

 Pyrite (FeS 2 ) ... -53 

 Specific gravity ... 2 '8 9 3 



(/.) Diabase. 



The only instance which I have met with of a rock which 

 did not belong to the diorite group is that of a strong dyke 

 traversing the quartz-mica-diorites near the junction of the 

 Mount Elizabeth branch with Navigation Creek. Examined 

 in a thin slice, I found it to have the following composition : — 



(1.) Iron ores in crystals showing rhombic sections, and 

 all more or less surrounded by a grey, somewhat obscure, 

 material (leucoxene). 



(2.) Plagio-felspars extended in the direction of the 

 brachypinacoid, and compounded according to the Albite 

 law, more rarely the Pericline law in interposed lamellae. I 

 could not obtain any satisfactory measurements of the incli- 

 nation of the plane of vibration. The larger crystals have 

 their edges and corners rounded off. 



(3.) Pale yellow augite in ill-formed crystals and groups 

 of crystalline grains. Some of this augite has been con- 

 verted into a pale green chloritic mineral, and much more 



