USGS Professional Paper 144 p 177-178
LODES OF THE HANCOCK MINE
Production from the lodes of the Hancock mine (pl. 35) began in 1861 and continued with interruptions till 1918. The total production from these lodes, together with a considerable production from the Pewabic lodes by the Hancock Consolidated Mining Co. that has not been separated is 17,559,557 pounds. The earlier production, from 1861 to 1886, 5,360,000 pounds, was derived from lode No. 1; and the later production, from 1911 to 1918, 12,199,000 pounds, mainly from lodes Nos. 3 and 4 and the Pewabic lodes. In the later years the yield averaged about 13.5 pounds copper to the ton.
The writers had no opportunity for an examination of the Hancock mine, and the following statements and the accompanying maps and sections are based on data furnished by the Hancock Consolidated Mining Co.
The lodes of the Hancock mine lie between No. 17 conglomerate and the Pewabic lodes. The old No. 1 lode is, to judge from the descriptions and from the course of the drifts along it, apparently on the Hancock fault, a reverse fault which strikes at the surface about N. 54° E. and dips at a considerably steeper angle than the beds. The fault fissure evidently curves very irregularly, both the dip and strike varying greatly from place to place, and it doubtless has numerous branches. The apparent displacement of the beds, measured horizontally at right angles to the strike, is about 600 feet but differs considerably at different points. The actual movement on the fault to produce this apparent displacement was certainly much greater.
No. 1 lode has been opened along the strike for about 1,200 feet and to the fourteenth level. Most of the stoping was done between the surface and the tenth level. There is a strong suggestion of a southerly pitch to the ore shoot.
No. 3 lode is the amygdaloid of the third flow below No. 17 conglomerate and is therefore at the general horizon of the Ashbed amygdaloid. It is, in places at least, scoriaceous and in this respect resembles the Ashbed. The No. 3 lode has been opened for about 1,500 feet along the strike and has been stoped mainly between the tenth and eighteenth levels.
No. 2 lode is the amygdaloid next below No. 3 lode. The lode called No. 9, above the eighteenth level is probably No. 2 repeated below the Hancock fault. No. 2 lode has been opened for about 1,000 feet along the strike and stoped mainly between the sixth and eleventh levels. The stoping on the part known as No. 9 is mainly between the twelfth and eighteenth levels.
The true No. 9 lode, as it may be called, below the eighteenth level is above the fault and below No. 16 conglomerate. No. 4 lode is a little below this No. 9 lode and probably a little above the Pewabic Far West lodes.
There are, then, two general horizons of mineralization - one represented by lodes No. 2 and No. 3, lying near the horizon of the Ashbed amygdaloid, and the other represented by No. 4 and the true No, 9 which lie below No. 16 conglomerate. In addition No. 1 lode is apparently on the Hancock fault. Most of the ore thus far developed occurred above the Hancock fault.
Collector's Corner Previous section Table of Contents Next section