BY F. D. POWER, F.G.S. 29 



ably close, dense texture. The boundary between this 

 pyrites and the hematite is very sharp, which is what we 

 would expect if due to the cause I suggest ; for if such a 

 settling down of the mountains on each side took place after 

 the hard hematite was segregated, there being little cohesion 

 between the hematite and the softer schists, a rupture would 

 most easily take place between them ; and the hematite, not 

 yielding so readily to pressure exerted end on to its grain, 

 would break up into fine particles that could occupy any 

 loosened portion of its body ; while the country rock, being 

 more flexible, would bend rather than break, and so remain 

 porous until infilitrated mineral solutions filled up all the 

 spaces. The country rock about the iron pyrites deposit 

 occurs at various angles of strike, as if wrapping round it, 

 and the talcose schist illustrates the lenticular nature I have 

 tried to describe on a small scale. There are no signs of 

 sudden rupture having taken place here, but everything 

 points to a gradual motion, which in all probability is 

 continued at the present day. Associated with the iron 

 pyrites we find galena ; also copper pyrites, with its resulting 

 secondary minerals — viz., malachite, azurite, cuprite, and 

 native copper. The pyrites deposit occupies a depression or 

 gully running 25 degrees W. of N., the hollow evidently 

 being formed by the decomposition of the pyrites, a large 

 portion of it being dissolved out by water in the form of 

 sulphate of iron, while that which is oxidised into gossan 

 remains behind as a thin capping, until denuded by atmos- 

 pheric agencies. I account for the pyrites being found so 

 near the surface by the fact that the country here is very 

 moist, a peaty water oozing out of the button grass, the 

 reducing action of which would retard oxidation. I also 

 eredit this water with "being the agent that reduces the silver 

 and copper which we find in the neighbourhood. The water 

 is so darkly coloured that one almost suspects Neptune of 

 having upset his billy-can of tea. The mass of the pyrites is 

 very poor in gold, but the gossan (specimen 559) or iron 

 capping in places contains a fair amount. This is only 

 reasonable, for a ton of gossan is greater in bulk than a ton 

 of heavier pyrites, and since a ton of gossan must be the 

 product of decomposition of much more than a ton of pyrites, 

 the former will naturally contain the gold concentrated in it, 

 unless washed away mechanically, but the vesicular nature of 

 the gossan tends to prevent that, and the sulphate of iron 

 formed would prevent it being carried away in solution 

 chemically. The decomposed pyrites, when placed on litmus 

 paper and moistened, shows a distinct acid reaction, and this 

 stone, when passed through the battery, unless well leached 

 first and washed with alkaline water, will eat into the plates 

 and sicken the quicksilver. 



