1866.] 



BATJERMAN COPPER-MINES OP MICHIGAN. 



457 



impregnated with copper to a depth of about 20 feet from the lodes. 

 The mine is 156 fathoms deep, and produces from 35 to 65 masses 

 weighing about a ton each per month, and about an equal weight 

 from stamp-rock, containing about 1-9 per cent. The copper-ground, 

 as a rule, appears to follow the greenstone in depth, dipping about 

 27° north-westerly. The North and South Cliif mines, opened on 

 the prolongations of the same lode, are not now at work. 



The Central mine, about 14 miles east of the Cliff, is opened upon 

 a similar lode, consisting of a series of alternations of red laumonite 

 strings, with large lenticular expansions containing copper. The 

 original discovery of this lode was made in an old Indian working at 

 the 'No. 2 shaft, out of which a mass of copper, weighing 50 tons, 

 was taken. Only a small amount of metal has been found imme- 

 diately below this point in sinking ; but further north, below the 

 greenstone, under similar conditions to those observed in the Cliff 

 mine, a very rich run of ground has been discovered. There is a 

 good deal of calcspar in the vein, and the finer copper appears rather 

 in sheets than in shots. At the 50-fathom level, on the No. 4 shaft, 

 the largest mass that has as yet been discovered on the lake was 

 struck ; it measured 50 feet in length, 30 in height, and about 4| 

 feet in greatest thickness, and yielded somewhat over 500 tons of 

 copper. 



Pig. 5. — Longitudinal Section of the Central Mine, 



No. 1 Shaft. No. 2 Shaft. N. 15° W. No. 4 Shaft. 



The mines in the range north of the greenstone are the Petherick, 

 Copper PaUs, and Phoenix, which derive their produce almost entirely 

 from a remarkable bed of very much decomposed finely vesicular 

 trap, filled with small shots of copper, known locally as the " ash- 

 bed." Associated with this is a compact trap, containing elongated 

 cavities at its contact with the more vesicular portions. These 

 cavities are usually filled with copper in ramifying forms resembling 

 eagles' claws. The ash-bed, according to its discoverer, Mr. Hill, 

 has been traced for about 8 miles, and by its position probably 

 represents some of the upper beds of Portage Lake. Although ex- 

 tensively worked, it is too poor to yield any great profit, the produce 

 at Copper Palls being 1 per cent., and at the Phoenix only | per 

 cent., of the rock treated. 



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