GEOLOGY OF THE GLOUCESTER DISTRICT, N.S.W. 



257 



mineral may represent small one-time ferro-magnesian 

 minerals; the total amount of such material is however 

 very small. The chemical analysis given here was made 

 from a specimen obtained in the Gap about a quarter of a 

 mile south of the Gloucester Trig. Station, and from near 

 the top of the Kuttung Series. 



Chemical Composition. 



Si0 2 



77-76 



A1 3 3 



9-94 



Fe 2 3 



1-15 



FeO 



0-59 



MgO 



0-18 



CaO 



0-24 



Na 2 



0-86 



K 2 



7-75 



H 2 (100° C.) 



0-38 



H 2 O(100°C.+ 



) 1-00 



C0 2 



0-30 



Ti0 2 



0-15 



Zr 2 3 



absent 



P 2 5 



0-03 



Norm. 





Quartz 



42-60 



Orthoclase . . . 



45-59 



Albite 



7-34 



Anorthite 



0-28 



Diopside 



0-86 



Magnetite 



1-39 



Ilmenite 



0-30 



Hematite 



0-16 



so 8 



absent 



CI 



trace* 



S(FeS 2 ) ... 



absent 



Ca 2 O s 



absent 



NiO and CoO 



absent 



MnO 



0-02 



BaO 



0-02 



SrO 



trace* 



Li0 2 



absent 



v 2 o 5 



absent 



Total ... 



100-10 



Specific gravity 2-582 



Classification. 

 Class I. Persalane 

 Order 3 Columbare 

 Rang 1 Alaskase 

 Sub-rang 2 Magdeburgose 

 Magmatic name Magdeburgose 



This rock is obviously a typical potash rhyolite and con- 

 tains nearly 96% of salic molecules. In the table of rock 

 analyses on page 261 analyses of Kuttung lava flows from 

 Mount Bright near Pokolbin and from Paddy's Hill near 



Q— December 7, 1921. 



