Se 
J. D. Whitney on Minerals of the Lake Superior region. 11 
_ Chrysocolla.—Handsome specimens are found in the Copper 
Falls vein, forming delicate stalactitic incrustations on the vein- 
stone, and sometimes coating the crystals of analcime. 
Chaleopyrite—V eins of quartz containing this ore are numer- 
ous in the trappean rocks of the Azoic series, in the neighbor- 
hood of Echo Lake, about 15 miles east of Saut St. Marie. Co 
per pyrites is the predominating ore at the Bruce and Wellington 
mines on Lake Huron: it has also been found in veins in the 
uron Mts., on the south shore of Lake Superior, where no 
mining has yet been carried on. 
per.—The native metal is now the exclusive object of min- 
phurets, however, are still mined on Lake Huron, in the Azoi¢ 
rocks, a formation which has not been proved as yet on either 
shore of Lake Superior, to contain any workable vein of the 
native metal. 
The largest mass of copper yet discovered on Lake Superior 
was in the 10-fathom level of the Minnesota mine, on the so- 
called “conglomerate lode,” or the copper-bearing vein which 
thirty months.* . 
Almost all the specimens collected on Lake Superior as erys+ 
tallized copper, are, in reality, not actual crystals, but only imita- 
tive forms produced by juxtaposition with the crystalline faces 
of some mineral substance, and usually of caleareous spar. The 
large masses which are seen in collections, and labelled “‘crys- 
tallized copper from the Cliff mine,” usually exhibit only a few 
indistinct planes which can be referred to the crystalline force 
of the metal itself. vet 
The finest groups of crystals ever obtained in the copper rée- 
ion were from the Old Copper Falls mine, a locality which has 
ong ceased to be worked; and no other has furnished any speci- 
mens to compare with those found here. 
ne form in these groups was the rhombic do- 
decahedron; but the octahedron was not of unfrequent occur- 
size of the pieces into which the great masses are cut for convenient hand- 
ling under ground and shipment is now much greater than it was formerly: blocks 
of copper weighing from 5ovo to 9000 pounds are not unfrequently brought to the 
surface and sent off to the smelting works. 
- 
