94 BULLETIN 12, UNITED STATES NATIONAL MUSEUM. 



stopped before the cast has been completed, leaviug an outside shell 

 of copper with crystals and crystalline masses projecting into the open 

 center. 



The conglomerate bed is traversed by a great many fissures running 

 in every direction, and causing a great deal of faulting, which adds 

 seriously to the difficulties of mining. Some of these fissures are filled 

 with calcite, forming true veins, while others are simply filled with 

 clay. The faulting produced by these fissures is generally small, but 

 owing to their number they are very troublesome. The clay fissures 

 or slips simply fault the strata, while the calcite veins not only fault 

 the strata, but also terminate the copper-bearing layer. Within the 

 copper-bearing layers the copj)er is more or less concentrated, forming 

 rich chutes, and there are several of these chutes. 



A plan of the mine is shown in PL. x. 



The following are characteristic sami)les of the ore : 



(1) Free copper, coated with oxidation products, surface or float copper. (54743.) 



(2) Conglomerate, AA'itli much free copper. The blackened copper of this speciuieu 

 is characteristic of the ore above the water level, 400 to 500 feet. (54729.) 



(3) Conglomerate, fine-grained, containing much free copper. From the eastern, 

 chute between the first and second levels. (54740,) 



(4) Conglomerate, coutaiuiug much free copper which cements the pebbles. 

 (547.30.) 



(5) Conglomerate, very coarse, with free copper. (54674.) 



(6) Conglomerate, very coarse, with free copper and some calcite. (54651.) 



(7) Conglomerate, coarse, with free copper. (54726.) 



(8) Conglomerate, coarse, with free copper. (54733.) 



(9) Conglomerate, containing considerable sand with free copper. (54727.) 



(10) Conglomerate, containing much sand with much free copper. (5472d.) 



(11) Free copper, a small mass. (54680.) 



(12) Free copper, coated with crystals of calcite. From one of the fissure veins. 

 (54G87.) 



(13) Trap rock, carrying a little free copper. From northwest vein, 10 inches wide. 

 (54663.) 



The following five samples represent the characteristic barren con- 

 glomerate and sandstones : 



(1) Conglomerate, ordinary, compact. (54682.) 



(2) Conglomerate, ordinary, compact, showing some calcite. (54681.) 



(3) Conglomerate, ordinary, compact, with amygdaloid pebbles. (54665.) 



(4) Sandstone, with a few pebbles, from a 6-inch layer. (54688.) 



(5) Sandstone. (54673.) 



To illustrate the formations exposed by the mining operations a 

 complete section of the bed, taken from the crosscut 100 feet east 

 of No. 1 shaft, is first shown. The whole width of the bed at this 

 point is about 30 feet and presents some peculiarities. It has no sand- 

 stone layers and in general is more open in the upper levels than in the 

 deeper portions of the mine. There are two copper bearing lasers or 

 chutes, the lower one being thicker and more valuable : 



(1) Trap rock, very much decomposed and friable, from a bed 7 feet thick, between 

 the greenstone and the conglomerate. A 2-inch streak of chiy separates this trap 

 from the conglomerate. (r)4689. ) 



(2) Conglomerate, from the top of the bed, showing the contact. (54677.) 



