Mine Geology and History

The ground on which the Iron Mountain deposit occurs was owned by Mr. W. H. Boyer, of Salida, and Mr. E. Frankenberry, of Canon City, and was being developed and operated by Mr. Boyer. The two claims are in Wells Canyon at an altitude of 7700 feet. The claims were located January 1, 1916. The property is located two miles northeast of Wellsville, a station on the Denver & Rio Grande Railroad, six miles east of Salida. From the railroad to the mine, the wagon road ran up a steep narrow gulch, but the roadbed was good. The ore occurs in massive limestones— probably of the carboniferous age. The region has undergone considerable folding and as a result, the beds dip in an easterly direction at angles from 20 to 40 degrees.

On either side of this area, a short distance away, are found the old pre-Cambrian formations, consisting of slate, schist, gneiss, and quartzite, and overlying the sediments are extensive rocks of more recent age. The ore occurs as an irregular bed between two beds of limestone.It follows quite closely along the bedding, although the contact with the lower bed is irregular.As a result, it is inclined to be pockety and irregular, varying in thickness from twelve inches to four feet.  This pinching and swelling gives rise to the formation of pockets, which may contain forty or more tons of good ore. The ore itself consists largely of pyrolusite and psilomelane with mixtures of wad.  It is possible that more or less manganite is mixed in with the pyrolusite.  In places the ore is crystalline and fibrous, and here and there one finds little cavities lined with botryoidal psilomelane.  Pyrolusite or wad forms the center of rod-like growths or concretion, and the outer shell is hard psilomelane.   The greater part of it, however, is granular and soft.  In the cavities are seen alternating bands of compact psilomelane and fibrous, crystalline pyrolusite.  In places there are little nests or cavities filled with a granular white calcite.  Around the cavities there is usually a zone of rather porous material, as if solution had removed some of the constituents.The ore was probably derived from manganese-bearing minerals in the metamorphic rocks of the region.  Upon weathering, it was carried out and deposited, either in disseminated form or directly concentrated into its present form.  Its position in the limestone rather favors the latter alternative, and furthermore suggests the possibility of a slight local unconformity.  If this is the case it would seem that the concentration took place in a relatively small shallow basin which was gradually sinking.  The irregular contact with the limestone below seems to suggest unconformity.  There is no evidence at hand .that the ore is of a residual character, while the small amount of replacement in evidence probablyoccurred subsequent to the deposition of the ore in its present form. The ore body has been opened by a forty-foot inclined winze and a seventy-foot tunnel about thirty feet below the bottom of the winze.  Several carloads of ore were taken from these openings and shipped to the Colorado Fuel & Iron Company, to be used in the manufacture of steel.  There was in sight at the time of examination from 3,000 to 5,000 tons of ore, that would run from 20 to 40% manganese.  It is entirely possible that by working farther along the outcrop of the deposit considerably more good ore could be discovered.

The analysis of an average sample of ore taken from material the stock pile ready for shipping gave the following results:

          Mn      40.00%            Fe      3.6%            SiO2      4.0%
          P           0.03%            S        0.7% 

From this analysis, the ore comes well within the limits of silica, phosphorous and sulphur as set by the smelter.  By selective mining and sorting, a better grade of ore could be produced. A second bed of ore is found about fifty feet higher stratigraphically than the one described.  It is much thinner and is more irregular than the first one.  It can be traced for a considerable distance along the hillside.  Possibly if it were opened up some good ore might be obtained.

*The Above information Reprinted  from USGS Bulletin 715, "Contributions To Economic Geology" 1920.