300 PROCEED rSTGS OF THE GEOLOGICAL SOCIETY. [April 24/ 



Metamorphic. 



The mineral districts already opened in Queensland not situated 

 on areas. occupied by Palajozoic rocks of the Devonian epoch are : — 



1. Cape River. 6. Kilkivan. 



2. Portion of Gilbert. 7. Gooroomjam. 



3. Peak Downs. 8. Broughton. 



4. Cloncurry. 9. Etheridge, 



5. Black Snake. 10. Ravenswood. 



In each of these localities gold has been found in alluvial depo- 

 sits, resting on rocks of a metamorphic character, derived in part 

 from auriferous lodes, which traverse these strata. At the seven first- 

 mentioned diggings mica and hornblende schists are the commonest 

 forms of metamorphism developed ; while at the three latter the 

 mining-area is entirely confined to syenitic granite. 



An analysis of this rock from Ravenswood gave the following 

 results : — 



Silica 60-066 



Alumina 21-180 



Ferrous oxide 5-533 



Lime 4-833 



Magnesia 2-073 



Potash 2-120 



Soda 2-233 



"Water, constitution 1-305 



Water, hygroscopic 0-650 



99-993 



Its contained minerals were triclinic felspar, quartz, brown mica, 

 and a little hornblende, though some of the syenitic granites from the 

 same locality have a much larger percentage of hornblende. This was 

 a typical specimen of the hornblendic granites, largely developed in 

 various localities in Queensland, which evidently have been formed by 

 chemical and mechanical changes from stratified sedimentary rocks, 

 as evidenced by the occasional bands of mica- and other schists ob- 

 served in them at intervals. 



As far as my individual observations are to be trusted, all the 

 granites of the colony that contain hornblende in addition to mica, 

 and the greater proportion of whose felspar is triclinic, may be 

 classed among the metamorphic series. 



The decomposition of such granites forms fair soils, yielding good 

 grasses ; and their physical aspect is that of an undulating country, 

 with gently sloping ridges ; and -as a whole they are favourable to 

 the production of other metallic minerals besides gold. 



"What has been asserted as to the value of certain trappean rocks 

 in influencing the production of mineral lodes in the Devonian 

 system, is also borne out in several of the localities enumerated 

 above, included within metamorphic areas. 



Whilst, however, the mineralizing traps of Devonian areas are 



