USGS Professional Paper 144 Butler & Burbank pp 221-223

     SUPERIOR LODES

     OCCURRENCE

     The main Superior lode (pl. 48) is approximately at the same horizon as the Baltic lode and may be identical with it. It has been developed by the Superior Copper Co. and the Houghton Copper Co. Between the Superior mine and the Copper Range Co.'s mines, to the south, on the Baltic lode, are the Copper Range Co.'s Section 16 explorations, which are in a zone of considerable faulting, and no positive correlation of the beds has been carried across this zone.

     Here as on the Baltic lode, both a main lode, called the Superior lode, and a west lode, called the Superior West lode, have been worked. The main lode has been opened in the two mines for a horizontal distance of about 6,000 feet and down to the thirty-first level in the Superior mine and about the fourteenth level in the Houghton Copper mine.

     PRODUCTION

     The following table gives the result of operations on the lodes to the end of 1925.

 Production and dividends from the Superior lodes, 1906-1923

     CHARACTER

     The main Superior lode, as indicated by the material on the dumps of the two mines and from descriptions, is a fragmental lode of distinctly scoriaceous character, with some shaly to sandy rock above the lode in the Superior mine.

     The Superior West lode where mined is prevailingly fragmental but contains areas of cellular top. Outside of the main ore shoot the fragmental areas appear to be small as compared with the cellular.

     MINERALIZATION

     The most abundant minerals associated with copper in the Superior West lode are quartz, pumpellyite, epidote, calcite, and feldspar. Feldspar is unusually abundant in this lode, as contrasted with its scarcity on the Baltic lode. Laumontite is present in fissures and locally in the lode. Chalcocite and barite are present in small amount in fissures crossing the lode. The writers had no opportunity to examine the main Superior lode.

     ORE SHOOTS

     The ore shoot in the main Superior lode was developed in the Superior mine from the surface to the nineteenth level, but little of it was mined below the seventeenth level. The productive ground extended for 1,200 to 1,500 feet along the strike, but less than 50 per cent of the lode within the shoot was mined for ore. The general pitch of the shoot in the lode was to the north.

     In the Superior West lode a shoot pitching south at a low angle was opened from the twelfth to the thirty-first level, but most of the ore mined was obtained between the twelfth and twenty-third levels. This shoot was developed along the strike for 1,000 to 1,500 feet, and in the most productive part between the twelfth and eighteenth levels a rather high percentage of the lode was mined. In the lower levels the shoot was small and "bunchy."

     In 1920 the mine was closed, and the management stated that ore reserves had been exhausted and that prospecting for new ore had not been sufficiently encouraging to warrant further expenditure.

     The Houghton Copper mine is north of the Superior mine, and the main openings are thought to be on the main Superior lode. The shaft is in the foot of the "East lode," which is probably the main lode. There has been some development in the upper levels on a lode lying farther east, and the Superior West lode has been opened in the Houghton ground to a slight extent by a drift from the nineteenth level of the Superior mine.

     Only relatively small areas of the lode were stoped. The discard of rock broken in 1912 was 41 per cent, and the copper yield was low.

     ISLE ROYALE

     On the Isle Royale property an amygdaloid at the horizon of the Baltic lode has been opened by the A and Section 12 shafts, but without encouraging results.

     FELSITE OF INDIANA MINE

     DEVELOPMENT

     The No. 1 Indiana shaft was begun in 1910 to explore an area of felsite which had been cut in diamond-drill hole No. 2 and from which a very rich core had been taken at a depth of about 1,400 feet. This exploration was carried on till 1916. The shaft was sunk below the fourteenth level, and openings were made at the 600-foot, 1,150-foot, and 1,400-foot levels.

     The results of this work indicated that the felsite is an irregular body intruded into the traps. The felsite on the dump is a reddish fine-grained rock with scattered phenocrysts of quartz and feldspar. It is all much shattered, and there is also much felsite breccia, which probably came from the vicinity of the contact with the trap, where a considerable part of the exploration was carried on.

     MINERALIZATION

     Calcite is everywhere present along seams in the rock, and the felsite is bleached to a light gray. In some of the rock this bleaching has included the whole area between fissures. Oxidized copper minerals, carbonate (malachite), and silicate occur along many of the fissures. Where the oxidized minerals are present the original minerals have usually been entirely altered, but in some of the least altered portions chalcocite and "brittle" arsenical copper are present. It is probable that the oxidized minerals have been derived from both of these. In the larger fissures rather massive copper was found. There are masses several hundred pounds in weight on the dump.

     No. 2 drill hole, from which the rich core was taken, was not identified underground, but the management believed when operations were suspended in 1916 that the core had come from a mineralized fissure or vein, like those encountered in the workings, and that the vein was probably not of great extent.

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