ORE DEPOSITS IN MAN8FIELD SLATE. 67 



districts of tlie Lake Superior region. The ore was first found in a test pit 

 wliicli passed through 9 feet of drift. The main working shaft was then 

 located about 100 feet west of this point. It was put down to a depth of 

 460 feet before ore was struck. From this shaft crosscuts were driven east 

 at average intervals of 70 feet, and the ore body was met at a distance vary- 

 ing from 74 feet at the first level to 10 feet at the sixth level. The cross- 

 cuts, in every case after leaving the greenstone, pass through so-called red 

 slate, at the maximum about 25 feet thick, before ore is reached, this rock 

 constituting the hanging wall. From these data the dip of the ore body 

 may be calculated to be about 80° W., agreeing well with the observed dip 

 of the slates, which outcrop over the area. The thickness of the ore, as 

 shown by the cross sections, averages about 25 feet. The extreme variation 

 in thickness ranges from two sets, or 16 feet, to four sets, or 32 feet. The 

 strike of the slates is north and south, and the trend of the ore body 

 agrees with this. This brings its southern end under the original course 

 of the Michigamme River as the stream bends slightly to the west, soiith 

 of the shaft. An examination of the longitudinal (north-south) section 

 through the ore body does not determine whether or not it has a pitch. 

 The southern boundary is nearly vertical from top to bottom, wliile the 

 northern boundary lengthens about 140 feet between the first and the fifth 

 levels. 



In the northern end of the mine — that is, in line with the strike of the 

 sedimentaries — the ore body terminates, in a more or less irregular wa}^, in 

 so-called mixed ore. This mixed ore continues to the north for over half a 

 mile, as shown by the numerous test pits which have been bottomed in it. 

 To the south of the mine shaft the ore body proper extends for 200 feet. It 

 then changes its character, becoming a lean non-Bessemer ore. A long drift 

 (335 feet) at the second level was run through this ore, and after leaving it 

 penetrated a mixed ore, the so-called lime rock (siderite?) and quartz rock 

 (chei't!) of the miners. Three crosscuts along this drift show the ore body 

 to vary from 20 to 30 feet in thickness, with the same foot and hanging wall 

 as for the remainder of the mine. The same condition exists also lower 

 down, as shown by a drift from the fourth level, 260 feet south. The 

 figures on PI. IX, giving longitudinal and cross sections of the mine, show 

 clearly the dimensions of the ore body. 



