CAEBONATE HILL. 411 



Pendery fault. — A slioi't distaiice west of the Glass shaft, a second fault, 

 apparently nearly parallel and having the same angle of inclination with 

 the Carbonate fault, cuts off the limestone, no explorations west of this 

 line having reached below the White Porphyry. Its probable continuation 

 has been traced southward to a connection with the Carbonate fault, and 

 northward through the Washburne and St. Mary workings, where it appears 

 to be accompanied by minor faults and folds, into a probable anticlinal fold 

 running north through the Niles- Augusta, and then northwestward, opposite 

 the Half Way House claim. 



Morning Star fault. — In the woi'lvings of the Momiiig Star mine a small 

 fault is found (shown in Section C, Atlas Sheet XXIX), in which the down- 

 throw is to the east. It is probably only local in character and corresponds 

 to the sharp bend in the beds observed in the Evening Star and Catalpa. 

 It was only obser-\'ed at one point, and is not therefore indicated on the 

 surface maps, as its direction would be purely hypothetical. 



Ore deposits. — The materials composing the ore deposits of Carbonate 

 Hill are essentially the same as those of Iron Hill ; the)' may perha2)S be 

 said to be poorer in bases of iron and manganese and proportioKately richer 

 in silica; therefore less favorable for the smelter; but this characteristic is 

 rather one to be confined to individual mines or parts of a mine than applied 

 in a general way. Silica occurs less frequently as chert and more com- 

 monly as a ver}' finely granular and somewhat porous quartz rock than on 

 either Iron or Frj^er Hill. The ore is either galena or its secondary prod- 

 ducts, carbonate of lead and chloride of silver. In one instance native 

 silver has been found. Dechenite, or the vanadate of lead, has been detected 

 in ore from the Evening Star and Morning Star mines by Dr. M. W. lies.' 



Exceptionally good opportunites are offered for observing the action 

 of replacement and the gradual passage from dolomite into the earthy 

 oxides of iron and manganese. The workings not yet having reached the 

 great distance from the surface that they have on Iron Hill, no such definite 

 e\idence is found of decrease in the action of surface waters producing 

 oxidation and chlorination of the original deposits. The limit of the zone 

 of oxidation would, moreover, be expected to be farther from the surface on 

 account of its lower altitude. 



'Americ.au Jourual of Science, May, 1682. 



