No. 6.] DOUGLAS — LAKE SUPERIOR COPPER MINES. 329 



arrangemeut of the copper, but one I had cut through the centre 

 was homogeneous in structure, but contained, embedded in the 

 copper, a few crystals of quartz and felspar. 



Interstratified with the conglomerate are thin bauds of copper 

 sandstone, the copper being in fine grains, sometimes deposited 

 pure, at others mixed with epidote and quartz or finely-ground 

 porphyry, the lamina? easily separable from one another. In 

 their midst are sometimes embedded pebbles of copper. Bands 

 of hard compact sandstone, from the disintegration of the same 

 rock as compose the conglomerate, are met with beneath the foot 

 wall, on the hanging wall, or in the bed itself. A specimen in 

 my possession exhibits successive layers firmly compacted, some 

 of conglomerate, others of coarse-grained and others of fine-grained 

 sandstone, with a surface distinctly ripple marked. The aqueous 

 origin of the bed cannot be doubted, but whether the copper was 

 mechanicjilly or chemically deposited, it is more difficult to 

 decide. The easier explanation of its occurrence is on the hypo- 

 thesis of a mechanical deposition, but, as militating strongly 

 against it, is the undoubted fact that the conglomerate pebbles 

 very rarely carry copper. The effects of subsequent chemical 

 action are beautifully exhibited in a clay Jiucaii which, from the 

 surface to nearly the lowest level driven, lines in places the foot- 

 wall. In it, embedded in soft clay, derived from the disintegra- 

 tion of the rock, and which harden into a mass that might almost 

 be mistaken for a piece of trap, occurs with calcspar, laumonite^ 

 and quartz, copper in dendritic masses, distinctly crystallised. 

 Some of the specimens taken from the flucan undoubtedly ex- 

 hibit instances of false crystallisation, plainly showing the impress 

 of the crystals amidst which they were formed, but others are 

 as undoubtedly themselves crystallised. Vugs also occur lined 

 with crystals of epidote, and calc spar, and spongy copper; and 

 through the bed there passes diagonally what is called a dropper. 

 It is only a few inches wide, but consists of what is locally called 

 brick copper, which is accompanied by crystallised silicated 

 minerals, entangled in which are conglomerate pebbles. It has 

 unmistakable si icken sides, on which the copper is actually polished. 



A bed of amygdaloidal trap overlies the conglomerate, and is 

 in places rich in copper. Some of the amygdules are completely 

 filled with copper, in others a small nucleus of copper is enveloped 

 in calc spar or epidote, while a coating of red ferruginous-looking 

 earth lines the cell. A trap, similar in appearance, is worked 



