302 PKOCEEMNGS OF THE GEOLOGICAL SOCIETY, [April 24, 



" The tin crystals are principally associated with the quartz in 

 the most highly micaceous portions." 



And, speaking of the alluvial drifts from these stanniferous 

 granites, he adds : — 



" Their richness and continuousness is extraordinary, and, I should 

 thinJc, quite unpaixdieled in any other country." 



In the metamorphic system, indeed, is the most varied development 

 of metallic ores in Queensland ; in it also the greatest number of 

 " true lodes " have been found ; and this fact affords the best reason 

 for the supposition that the comparatively unexplored districts at 

 the heads of the Mitchell and in the McKinlay ranges, where large 

 tracts of metamorphic rocks are known to exist, will yet add very 

 much to the mineral exports of Queensland when thoroughly pros- 

 pected. From the exploring expedition about to start into the 

 former of these districts great results may be expected. 



Geajsttic, 



Outcrops of granite extend along the eastern coast of Queensland 

 from Cape York nearly up to Broadsound, and inland as far as the 

 heads of streams running direct from the inner coast rang-e to the sea. 



Isolated patches of the same character of rock are found at 

 intervals fi'om the seaboard back to the coast range, going south 

 fi'om Broadsand. 



Very little rock of this character is met with west and south of 

 the dividing range which separates rivers flowing to the eastern 

 and northern coast and those trending south to the Murray or 

 Coopers' Creek. 



In their lithological character, the granites of Queensland vary 

 very much in their crystalline texture and arrangement of minerals 

 in the same rock-masses, passing from true granites into porphyry 

 and quartz-porphyry; but the monoclinic felspar is always in 

 excess of the triclinic. 



With the exception of molybden-glance, found in the porphyry 

 near Townsyille, no metallic ores are associated with the granites 

 proper. 



Teappean. 



In a previous portion of this paper much stress has been laid on 

 the value of certain intrusive Trap-rocks as specially influencing the 

 production of auriferous veinstones in Queensland ; and it is now 

 proposed to investigate this subject somewhat more in detail. 



The petrology of these may be divided into four type classes : — 



1. Pyritous porphyrites and porphyries. 



2. Pyritous diorites and diabases. 



3. Chrome-iron serpentines. 



4. Pyritous felsites. 



Group 1. 



The analysis of a characteristic specimen of a porphyrite of Group 1 

 (PI. XI. fig. 2) gave the following results : — 



