198 NOTES ON THE MOUNT LYELL MINE. 
of the deposit, and the magnitude of the entire scheme, 1,000 tons of 
ore daily should be treated, yielding, say— 
50 tons copper, worth £44 per ton ... aks ... £2,200 
3,0000z. silver, worth 2s, 6d. per oz. oe an 375, 
3,000dwt. gold, worth 4s. per dwt ... a ae 600 
Making adaily outputof ... aes i ... £8,175 
This paper is not intended to touch at all upon the commercial aspect of 
the mine, and | only mention these few facts, that have already been 
made public in my report, for the satisfaction of those who cannot under- 
stand how such low grade ores can be made to pay. I cannot possibly 
go into details of cost or treatment of the ore, but to furnish a clue to 
those who may desire to make their own calculations, I will state that 
the one important item of cost in the entire treatment is the cost of 
smelting the ore. The mining will be done by open quarrying for 20 
years. The stall-roasting of similar ore has not cost me ls. per ton 
any time in the past 16 years—reduced to Tasmanian wages and con- 
ditions. The bessemerising and remaining operations come solely on the 
matter, so that they are reduced to a very small sum for each ton of 
ore, but the smelting comes on the original roasted ore, and is always 
the heavy expense. A modern water jacket will put through 100 tons 
of ore daily, per 24 hours, will require five men per shift, and 1 ton of 
coke to each 7 or 8 tons of ore. As the company possesses a water 
power far beyond the needs of all its machinery, very little need be 
added for blast. From these rough statements it will be seen that even 
the smelting cost need not be very alarming, when executed on this 
large scale. To return to our proper subject. There is yet one point 
more that I have to speak of, and it is in this point that the Lyell mine 
is unique. In all points—except its unusual richness and width—it is 
almost precisely like scores and hundreds of similar pyrites deposits in 
other parts of the world. All have the same decomposed gossan on top, 
except where glacial or other causes have scored them clean. All are 
richer in gold above than in pyrites below, and all that contain gold 
invariably run into pyrites in depth. All, or nearly all, have the same 
sinter and iron-ochre amongst the gossan in places that makes inex- 
perienced people regard them as geysers or hot springs, when in reality 
this phenomenon is simply a secondary metamorphosis of the gossan. I 
have even been told that some geologists have pronounced these 
characteristically aqueous deposits as volcanic, and the heavy spar a 
result of sublimation. But I am not willing to believe this, for surely 
every geologist knows that heavy spar is one of the few substances that 
are absolutely non-sublimable, and can only be formed by aqueous solu- 
tions, whilst iron pyrites is bi-sulphide ; that even if there were no air 
present to roast it, would at once lose one atom of sulphur on the slightest 
approach of heat, and become a mono-sulphid magnetic-pyrites, whilst 
the sublimed sulphur would be deposited in the crevices of the rocks. 
But it is as idle at the present day to argue in favour of the deposition 
of these deposits by the means I have described, as to waste time in 
trying to prove that the earth moves around the sun. Everybody who 
is familiar with these deposits- -and they are amongst the most common 
in many countries—is agreed as to their method of formation, and 
instead of their being unique, as I have heard one or two people call 
them, Mount Lyell and Mount Morgan, and similar deposits are the 
commonest and best known class of mines that we have. The infinitesi- 
mal extra percentage of gold that they happen to contain gives them an 
enormous commercial interest, but, geologically-speaking, they are 
almost too common and their mode of formation too well understood to 
be interesting. Where their wall rocks contain much felspar there are 
