SUPPLEMENTARY NOTE ON LIMURITE IN 

 TASMANIA. 



By W. H. Twelvetrees, F.G.S., and W. F. Petterd, 



C.M.Z.S. 



Since we contributed a notice* of the remarkable 

 ^' limurite" rock occurring on the property of the Cole- 

 brook Prospecting Association, N.E. Dundas, and more 

 recently discovered to extend in a more or less broken 

 sequence as far north as the Southern bank of the Pieman 

 River, mining operations have been carried on there 

 continuously, and have invested the occurrence with 

 additional interest from that point of view. Renewed 

 ■examination of the rock under the microscope, as well as 

 in the field, has resulted in further conclusions along the 

 line of our previous enquiries, and these we now submit. 



The mine has been made easily accessible from both 

 1R,ingville and Rosebery, being situate between those town- 

 iships. The rock occupies the saddle of a hill about 1500 

 feet above sea level, has approximately a strike of N.E.- 

 ;S.W., and has been proved to be metalliferous for at least 

 100 yards in width. The contained metals are magnetic 

 pyrites, arsenical iron pyrites, copper pyrites, and a 

 small amount of bismuth oxide, the copper combined 

 -with small gold and silver contents, giving the occur- 

 rence its chief economic value. The published assays 

 of the mixed stuff state the copper contents at fi'oni 

 1 °/q to 2 °/q. The Government Analyst is said to have also 

 ascertained the presence of 1 ° ^ of nickel and cobalt in the 

 pjTrhotite examined by him. 



Geologically, the rock is a dyke or intrusive mass, appa- 

 rently developed between slates on the eastern side and 

 terpentine on the west. The intrusion has evidently taken 

 place along or near this line of contact, though it would 

 appear to have come up at the top of the ridge through the 

 slates in several branches or bodies, as horses of hard meta- 

 morphic slate have been left standing in it, to the annoy- 

 ance of the miners. A clean contact is formed, near which 



* Proc Roy. Soc, Tasmania, 1897, pp. 1-6. 



