400 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



As regards the question of ore found along the fault plane, it may 

 readily be conceived that in the dragging movement of the edges of two 

 immense bodies of rock, the one against the other, during the fault dis- 

 placement, a very considerable amount of the adjoining rock could be broken 

 off and carried along for some distance from its original position. The 

 greater part of this material would be cla}' from the porphyr}', but with it 

 would be mixed a certain amount of limestone and ore. The circulation 

 of waters from the contact plane on either side, and therefore carrying more 

 or less mineral mattei- in solution, might occasion a secondary replacement 

 of this limestone by ore. It is even conceivable that in contact with the 

 inorganic matter, which must have been present, sulphates might have been 

 reduced to sulphides and galena have been deposited, but, unless the mineral 

 were found in the limestone outside of the attrition material of the fault 

 fissure, it would not be a proof that it was an original deposit before the 

 fault movement.^ 



'Iq the years that have elapsed since this was first prepared for the press, a uew shaft has heen 

 suuk 110 feet south of the Maiu iucline for the purpose of exploring the fault plane. The data ob- 

 tained from this by personal observation and from information furnished by Mr. F. T. Freelaud, 

 engineer of the mine, ^nd who was present during all the explorations, furnish a remarkable cou- 

 firmation of the above views. The shaft was suuk to a vertical depth of 30(i feet, but at an angle of 

 50° ; drifts were run on the fault plane at four levels, that on the second level having a total length of 

 a.OOO feet. In this level the sharp eastward bend of the fault plane has practically disappeared. On 

 the first level, which corresponds to the third level of the Main incliue, a considerable amount of ore was 

 obtained from the lower ore body. Ore was also obtained at various depths on the fault fissure below, 

 this level. In regard to this ore, the following facts were observed : First, the ore was always found 

 within the walls of the fault fissure; secondly, it occurred in masses rounded as if by attrition, and evi- 

 dently foreign to the clayey filling of the fissure in which it was imbedded; thirdly, no ore was found 

 outside of two vertical planes drawn through the intersection of the boundaries of the maiu Iron mine 

 ore body with the fault plane. It is interesting to compare the actual section obtained in this shaft 

 with that given in Section B, which was a theoretical deduction from data obtained at other points. 

 The angle of the fault was found in depth to average 50°, instead of 65", as had been deduced from 

 observations near the surface. 



Thictnesa of— 



Slide and White Porphyry 



Blue Limestone and vein material . 



Parting Quartzite 



Gray Porphj-iy 



Contact of White Limestone at . . 



McKeon 

 shaft sec- 

 tion. 



