From the numerous developments that have been made in the territory outside a circle, say, six miles in diameter, having the summit of Iron Clad Hill for its center, it would appear that no further extension of the ore-bearing district can be expected beyond the limits we now have.
This does not mean that all the mines are already opened, for very large tracts of territory within this circle remain undeveloped, in some of which new mines will assuredly be opened up. We have certainly not reached the end of new discoveries within the district.
A large impetus in this direction will be given by opening the properties of the Stratton Mining and Development Company to lessees, which is now expected very shortly.
The main question remaining is that of the permanence of the mines, and of this, during the past year, we have received very promising evidence.
The deepest mines now being worked on the different hills are as follows:
All but one of these shafts have good bodies of ore and excellent indications for the future at the lowest levels to which they have thus far attained. Certain of these shafts, to wit, the Last Dollar and Blue Bird, show some of the richest ore ever mined in the district at their lowest levels. It has lately been asserted that this great enrichment of these veins is due to secondary deposit. By this is meant that the gold values have been largely leached from the upper portion of these veins and redeposited at a lower level, thereby enriching the original ore deposit of the vein by this amount.
A special feature of these rich ore-bodies at 1,200 and 1,300 feet below surface is the presence of copper, which is entirely absent from the upper or oxidized portion of the Cripple Creek veins. Another change in the mineral contents of the veins at the greatest depth thus far attained is the presence of lead, zinc and antimony in sulphide form and an increase in pyrites.