1866.] BAUERMAN COPPER-MINES OF MICHIGAJT. 453 



condary planes. The finest crystallized varieties are, as a rule, ob- 

 tained from the Ontonagon district, and generally are more abundant 

 in newly opened mines than in those which are worked at greater 

 depths. 



In the Porcupine Mountains, to the west of the Ontonagon River, 

 a compact epidote rock is found containing copper in such a very 

 finely divided state, that it has hitherto been impossible to work it 

 advantageously. Native silver is found to a small extent, either 

 crystallized in arborescent forms, or irregularly spotted through the 

 copper, the line of separation between the two metals being well 

 marked in polished specimens. The Cliff" and Minnesota mines have 

 produced the largest amount of the precious metal, the absolute 

 production, however, being but small ; and scarcely any portion of 

 what is found comes into the hands of the mining adventurers, 

 except a few pounds which are annually got by hard picking from 

 the coarser sizes of the dressed mineral. The larger pieces find their 

 way into the hands of dealers and collectors, the earlier miners 

 having appropriated them to their own use, and the precedent has 

 been persistently followed ever since. 



5. Distrihiition and Association of the Copper. — Among the three 

 classes of deposits in which the mines are worked, the most important 

 are the stratified amygdaloids, which will therefore be first considered. 

 They are confined to the district of which Portage Lake (an inlet 

 which nearly cuts the Peninsula into two parts) is the centre. The 

 oldest mines are on the southern or Houghton side of the lake, so 

 called from the town or village named after the geologist who 

 examined the country ; while the newer and more important ones 

 are on the northern side, above the village of Hancock. The banks 

 of the lake on either side rise steeply from the water to a height of 

 from 400 to 600 feet ; the dressing-fiows, being placed close to the 

 water, receive the ores from the mines (which are located on the high 

 tablelands above) by means of railways and inclined planes. Taking 

 the extreme north and south mines as limits, the district has a 

 length, measured along the strike of the trappean belt, of about 9 

 miles, and a breadth of from 3 to 5 miles. The general section, 

 showing the position of the copper-bearing beds, is as shown in 

 Fig. 1. The series of beds indicated are amygdalous traps, which con- 

 tain more or less copper in the cavities, and are regularly mined under 



. Pig. 2. — Section from the Peiuahic Lode to the Albany and 

 Boston Conglomerate (530 feet). 



Albany & I ^ . fll4# 

 PewabicLode, Old Pewabic Green Amygdaloid Boston ^-^45 ^(2 c 2« 



12 ft. Lode, 32 ft. Lode, 19 ft. Lode, 7 ft. p^3 w ^ S Q § ® 



'J^Ml£^2y.d^^/^^ 



the name of " lodes." In the uppermost or Hancock series, only 

 one mine is opened, bearing the same name. The ground is more 



