418 GEOLOGICAL EXCLUSION TO THE UOCKY MOUNTAIN'S, 



LEADVILLE.« 



By 8. P. Emmons. 



This is the most important mining district in Colorado, and since the 

 falling-off in the production of the Oomstock, has been the greatest 

 silver producer in the whole West. Like so many other silver districts, 

 it owes its existence to the rest less wanderings of the early pioneers in 

 search of gold. Gold was discovered in the neighboring gulches in 

 I860; the richest portions of the placers were exhausted in a few years, 

 and the settlements that had sprang up around them were practically 

 abandoned. When, fifteen years later, it became generally known that 

 the heavy iron-stained stones, which had so much annoyed the gold 

 washers, were rich silver ores, a new excitement, or u boom," among 

 miners resulted; and, where in L878 a few scattered log houses were 

 all that were to be seen of human occupancy, in L880 already a city of 

 nearly L~>,000 inhabitants had sprung dp, with smelting works, banks, 

 theaters, and all the adjuncts of a prosperous mining center. The 

 town of to-day, though more substantially built, and with a population 

 which, though somewhat less numerous, has also a smaller proportion 

 of restless prospectors and adventurers and more substantial business 

 men, still shows many characteristics of that which lirst sprung into 

 existence with such marvellous rapidity. 



The valueof Leadville's product, in the thirteen years since it became 

 a silver camp, has been between one hundred and fifty and one hun- 

 dred and sixty millions of dollars. The annual product now varies from 

 ten to fifteen million dollars, the principal value of the ores being in 

 silver and lead, with a small proportion of gold. 



The city is situated at the western base of the Mosquito range, on 

 the upper edge of a gently-sloping mesa, about four miles east of and 

 (500 feet above the bottom of the Arkansas valley. This mesa is formed 

 of rudely-stratitied beds of coarse gravel and sand, washed down from 

 the adjoining mountains at the close of the first glacial period and 

 deposited in a lake which, at that time, filled the Upper Arkansas 

 valley above the present canyon at Granite. The moraines left by the 

 glaciers of the second glacial period extended out over these beds, and 

 their rearranged material, locally known as "wash," an unstratified 

 drift, covers the lower portions of the hills and the intermediate \ alley. 

 The depth of these successive gravel deposits immediately under Lead- 

 ville is 300 to 400 feet and upwards, 



