, 
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THE ORIGIN AND CLASSIFICATION OF ORE DEPOSITS. 203 
basis of this theory; yet it is difficult to see how any one can ascribe more than 
a local and insignificant effect to this cause. It is true that the action of water, 
as steam, is much the same as when fluid and highly heated, in the solution and 
transport of minerals; and the depusit of mercury ; sulphide of iron, and even 
gold, from the mingled water and steam of the California geysers proves this. So 
we may concede that steam has been an agent in the chemical solution and _pre- 
cipitation of ores; but this is a very different thing from the sublimation of the 
metals represented by these ores, and all knowledge and. analogy indicate that 
the silica which forms so large a part of vein-stones, and is so often seenin combs 
of interlocking crystals, has been deposited from an aqueous solution. But ar- 
gument is really wasted in a discussion of the filling of fissure-veins, since we 
have examples that seem to settle the question in favor of chemical precipitation 
from ascending hot water and steam. In the Steamboat Springs of Western Ne- 
vada, for example, we in fact catch mineral veins in the process of formation. 
These springs issue from extensive fissures which have been or are filling with sili- 
cious vein-stone that carries, according to M. Laur, oxide of iron, oxide of man- 
ganese, sulphide of iron, sulphide of copper, and metallic gold, and exhibits the 
banded structure so frequently observed in mineral veins.* 
In regard to the precise chemical reactions which take place in the deposi- 
tion of ores in veins, there is much yet to be learned, and this constitutes an in- 
teresting subject for original investigation, which I earnestly commend to those 
who are so situated that they can pursue it. 
It may be noticed, however, that the thermal springs which are now forming 
deposits like those in fissure-veins, contain alkaline carbonates and sulphides, 
and we have every reason to believe that highly carbonate alkaline waters contain- 
ing sulphureted hydrogen under varying conditions of temperature and pressure 
are capable of taking into solution and depositing all the metals and minerals with 
which we meet in mineral veins. 
To these necessarily brief notes on the filling of mineral veins should be ad- 
ded some interesting examples of the mechanical filling of fissures which have 
been recently brought to light in western mining. These are furnished by the 
remarkable deposits of gold and silver ore in the Bassick and Bull Domingo, near 
Rosita, Colorado, and the carbonate mine at Frisco, Utah. All these are appar- 
ently true fissure-veins, filled to as great a depth as they have yet been penetrated, by 
well-rounded pebbles and boulders which have fallen or been washed in from 
above. The porous mass thus formed has been subsequently saturated with a hot 
ascending mineral solution, which has cemented the pebbles and boulders to- 
gether into a conglomerate ore. In the Bassick, this ore consists of rich telluride 
of silver and gold, free gold, and the argentiferous sulphides of lead, zinc, cop- 
per andiron. In the Bull-Domingo and Carbonate mines, the cementing matter 
is argentiferous galena. That the pebbles and boulders have come from above 
is distinctly shown by the variety in their composition and the organic matters as- 
sociated with them. In the Bull-Domingo and the Bassick, the pebbles consist 
*Annales des Mines, Sixth Series, vol. iii, p. 421. 
