MINES OUTSIDE THE LEADVILLE DISTRICT. 525 



taken from it. Wheu the uuoxidized portion was reached, the ore became 

 poorer, yielding- only about six dollars per ton in gold, and the difficulty 

 of treating it in the ordinar}' stamp-mill was such that the mine was after 

 a few years practically abandoned. The ore body, which at the surface 

 had practically vertical walls, was found to split up in depth into smaller 

 bodies, dipping ea.stward and following approximatel}' the stratification 

 planes of the quartzite. On the east side of the open cut a body of por- 

 phyry forms the wall of the oi-e body for a sliort distance, and is probably 

 an offshoot from a larger body of Lincoln Porphyry which crops out in 

 the stream bed a few hundred feet below the mine. Explorations on this 

 ore body have been carried to a comparatively small distance below the 

 surface, and it is not at all improbable that, if systematically exposed in 

 <lepth, other large bodies might be developed, which, under present condi- 

 tions, with smelting works within easy reach, might be mined at a profit. 



Criterion mine. — Ou tlic uortli Wall of Buckskiu Caflon, a little above the 

 town of Buckskin Joe and about half way up the cliff, is the now aban- 

 doned Criterion mine. Here, just above the junction of the Lower Quartz- 

 ite with the underlying Archean, in a shallow ravine, is exposed a bod^' of 

 green porphyrite, impregnated with pyrites. A little above this, on the east 

 side of the ravine, is an immense open chamber, about sixty feet in height 

 by one hundred feet or more in length and ten to twenty feet wide, strik- 

 ing N. 35° E. It crosses the beds almost perpendicularly, and seems to 

 have once contained a body of ore, which has been removed either by 

 atmospheric agencies or possibly by some earlier miners of whom no trace is 

 left. The white quartzite adjoining the body is stained with iron oxide and 

 somewhat disintegrated. Nearly adjoining the upper part of this bod}' on the 

 northwest, an irregularly lenticular-shaped ore body has been developed by 

 the tunnel of the Criterion mine. Its form is rather horizontal than verti- 

 cal, but it connects with the upper part of the large cavity. The vein mate- 

 rial is crumbly iron-stained quartz, evidently resulting from the decompo- 

 sition of the quai'tzitg. The irregular-shaped chamber from which the ore 

 has been taken is in places twenty to twenty-five feet in height, and has 

 been opened for a length of over one hundred feet. No chemical exami- 

 nation was made of the ore to ascertain its actual value, but it contains 



