32 NOTES ON THE MOUNT LYELL DISTRICT. TASMANIA. 



most of the vegetation grew in situ ; well preserved samples' of 

 King William pine (specimen 563), and leatherwood (?) 

 (specimen 562), can in places be picked out, and sometimes 

 the ligneous matter has collected iron pyrites about it 

 (specimen 560). A little cement is now and again to be 

 met with : this in all probability was caused by pyrites being 

 formed, an opportunity being given to the iron present to 

 obtain sulphur from the decomposing vegetable matter, and 

 the more heavily charged water finding its way to the com- 

 paratively stagnant bottom would cement the pebbles 

 together. In course of time, as the deposit was drained, 

 this pyrites would become oxidised, as we find it at the 

 present day in Karlsen's face. Many of the streams on the 

 Mount Lyell side of the gully have been worked for gold, 

 until the heavy conglomerate boulders have become too 

 numerous to remove. Besides gold, native copper is also 

 obtained. 



Mount Lyell Copper Deposits. — On tracing the alluvial copper 

 to its source we are led to a zone of decomposed schists, forming 

 a pug — grey, yellow, and red — some hundred feet broad. 

 Where cut by the creeks this zone would appear to be equally 

 productive throughout, as the tenacious clay retains most of 

 the copper that is shed on to it ; but when we clean' up the 

 bed of the watercourses we find the copper is confined to 

 three distinct deposits, which run parallel, from two feet wide 

 downwards. Where the pug is comparatively dry, a little 

 below the surface, it flakes off in pieces corresponding to the 

 cleavage plains of the shale ; while the copper is found in 

 sheets, as if occupying the joints and cleavage plains of the 

 original rock. These sheets of metal, which at times are 

 fairly thick, get broken up into small nuggets, shots, and 

 spangles, which are more or less coated with the black oxide 

 of copper. Below the native copper we come across cuprite, 

 which occurs in beautiful crystals, mostly octahedrons, with 

 their edges truncated by faces of the rhombic dodecahedron. 

 !No doubt the native copper has been reduced from this by the 

 agency of the peaty waters. Still deeper than the cuprite we 

 come across copper pyrites, which takes upon itself the same 

 form as the rock which it impregnates ; in fact, it might be 

 termed a cupriferous schist. Instead of copper pyrites the 

 rock may be charged in a similar manner with iron pyrites, or 

 both. When the latter takes place the copper pyrites is 

 found concentrated on one side and the iron pyrites on the 

 other, and when the deposit crops out at the surface the iron 

 pyrites resolves itself into the oxide, which is sometimes accom- 

 panied with pyrolusite. 



In presenting the above remarks to the members of the 

 Boyal Society of Tasmania I have carefully weighed the ideas 

 •and opinions of others who have visited the locality I refer to. 



