508 GEOLOGY AliD MINING INDUSTEY OF LEADVILLE. 



inches wide, runuing no'theast, with a dip of 60° to the southeast. The ore 

 is a mixture of galena and pyrites, one lot of which yielded 22 ounces of 

 silver and 22 per cent, of lead to the ton. 



In the Green Mountain (E-12) mine the ore occurs in the sandstone, 

 and is a free-gold ore, sometimes very coarse. It was not accessible at time 

 of visit, and notliing certain could be learned of the form of the deposit, 

 which is very probably also a gash vein. 



LONG AND DERRY HILL. 



Ready Cash mine. — On the stccp south Wall of lowa gulcli formed by 

 Upper Long and Derry Hill is the Ready Cash mine, which is interesting 

 on account of its occurrence in Archean rocks rather than from its impor- 

 tance as an ore-producer. Its country rock is a coarse-grained, reddish 

 granite similar to that found at the heads of Iowa and Empire gulches. 

 The ore occurs in two small veins from one foot to four feet in width, which 

 come together at the surface. The one strikes N. 25° E. and dips 50° to 

 the east; the other strikes N. 45° E. and has a still steeper dip. The mine is 

 opened by tunnels which run into the hill in a southerly direction and cut 

 the veins at about three hundi'ed and twenty feet from the surface; in one 

 of the upper tunnels a dike of quartz -porphyry is cut between the two veins, 

 in which are some gold-bearing seams. The vein tilling consists principally 

 of altered granite, carrying free gold and some chloride of silver, with 

 relatively well defined walls. The deposit is evidently formed along fract- 

 ure planes in the granite, filling any cavity that may have existed and 

 replacing the constituents of the adjoining countr}^ rock. 



Long and Derry mines. — The Long and Derry mines were among the first 

 discovered in the Leadville region, and are still held by their original 

 owners, a very exceptional circumstance. They have been Worked very 

 slowly and irregularly, and at the time of examination no maps had been 

 made of the underground workings. Many of the drifts had become inacces- 

 sible, so that only a very general idea of the form of the deposits could be 

 obtained. They occur as a replacement of the Blue Limestone, but, as con- 

 trasted with the deposits of Iron and Carbonate Hills, rather in the form of 

 large chambers than along the contact with the overlying White Porphyry. 



