304 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 24, 



Of this Mr. Allport says : — 



" It contains a fibrous green mineral, which appears to be horn- 

 blende, partially altered ; the felspar is very opaque and indistinct 

 in form, 



" The base contains much chlorite and a few blebs of quartz, 

 together with a little epidote. 



"The rock is highly altered; and if the green fibrous mineral 

 should turn out to be uralite, it might then be called a diabase." 



All the rooks of this group, indeed, are much altered, generally in 

 the direction of serpentine ; their specific gravity varies from 2-700 

 to 3-100, according to the proportion of pyrites, hornblende, or 

 chlorite entering into their composition. The general facies cor- 

 responds with that of the intrusive dykes of the Wood's Point Dis- 

 trict, in Victoria, where similar geological conditions produce similar 

 mineral results. 



Group 3. 



Ghrome-iron Serpentines. 



The serpentines containing chromic iron, rarely pyrites, are in 

 my opinion simply altered forms of Group 2. 



In the Gladstone, Cawarral, and Kilkivan districts, there is con- 

 stant evidence of this ; and in the first-mentioned district it is espe- 

 cially marked. 



Group 4. 



Pyritous Felsite. 



This group is very sparingly represented in Queensland, the most 

 noticeable instance being that of Mount Wheeler, the analysis of 

 which by the late Professor Thompson, of the University of Sydney, 

 is as follows : — 



Mount Wheeler " Felsite." 



Undecomposed by HCl 96-75 



Decomposed „ 3-25 



Undecomposed. Decomposed. 



Silica 76-28 Silica 36-54 



Alumina 12-64 Alumina 23-97 



Ferric oxide 0-92 Perric oxide 11-59 



Ferrous oxide .... 0-85 Ferrous oxide none. 



Lime 0-33 Lime 1-57 



Magnesia trace Magnesia trace. 



Potash 3-30 Potash 1-14 



Soda .' 4-59 Soda 2-00 



Water 0-16 Water 19-98 



99-07 96-79 



Specific gravity 2-564. 



This rock rises abruptly to an elevation of 800 feet, through 

 serpentine, gabbro, and diaUage rock. It is very close-grained and 



