DENVER & KIO GRANDE WESTERN ROUTE. 



15 



was built near the spot where, in 1859, John H. Gregory made the 

 second great discovery of gold in this region.^ 



A few miles above Forks Creek the canyon becomes less rugged. 

 The first level bottom land the traveler has seen since leaving Golden 

 is occupied by the town of Idaho Springs (altitude 7,556 feet), which 

 is noted both as a pleasure resort and as a mining center. The waters 

 are mild solutions of carbonate and sulphate of soda and have tem- 



■^This discovery is described as fol- 

 lows by E. S. Bastin: 



In romantic interest and as a record 

 of human achievement in the face of 

 great difficulties the story of the dis- 

 covery and early development of the 

 mineral wealth of this region can 

 hardly be surpassed by any other 

 chapter in the history of the " win- 

 ning of the West." A decade after 

 the historic " rush " of the forty- 

 niners to California a second great 

 westward movement of gold seekers 

 from the Eastern States was started 

 by the discovery of gold in alluring 

 quantities near the present sites of 

 Idaho Springs and Central City. 

 It was first found in gravel on the out- 

 skirts of the town of Idaho Springs 

 by George A. Jackson, early in 1859. 

 A few months later the rich outcrop- 

 pings of a gold vein were discovered 

 on the present site of Central City by 

 John H. Gregorj\ These two discov- 

 eries precipitated a stampede of pros- 

 pectors, and within a few weeks many 

 of the richer veins of the region had 

 been discovered and many new de- 

 posits of gold-bearing gravel located. 

 This discovery began an era of min- 

 ing development that led to the foun- 

 dation and early growth of Denver 

 and of the State of Colorado. Up to 

 the end of the year 1918 there had 

 been added to the world's supply of the 

 precious metal from the counties of 

 Gilpin and Clear Creek alone approxi- 

 mately $175,000,000. Although the 

 period of maximum production was be- 

 tween the years 1870 and 1900, the 

 two counties still produce annually 

 metals to the value of more than 

 $1,000,000. 



The gold-bearing gravel was small 

 in quantity and was worked out 



mainly in the early years of mining. 

 Since then the gold has been taken 

 mainly from veins. Most of the veins 

 are steeply inclined and traverse schist, 

 gneiss, and granite, with which are 

 associated dikes and irregular masses 

 of younger intrusive rocks — the " por- 

 phyries " of the miners. The deepest 

 workings are those of the California 

 mine at Central City, whose shaft 

 descends 2,250 feet down a steeply 

 inclined vein. A few of the veins are 

 traceable on the surface continuously 

 for more than a mile, and most of 

 them are between 1 and 5 feet wide. 

 The principal metals won from the 

 ores are gold and silver, but copper, 

 lead, and recently zinc have also been 

 obtained. From a few of the veins 

 near Central City pitchblende or 

 uraninite, one of the minerals from 

 which radium is obtained, has been 

 mined, and this is the only locality 

 in the United States and one of the 

 few in the world at which the mineral 

 is found in commercial quantities. 



The ores are believed by geologists 

 to have been deposited by hot solu- 

 tions given off from buried masses of 

 slowly cooling "porphyry." The hot 

 waters at Idaho Springs have possi- 

 bly a similar origin, though their min- 

 eral content is probably much less 

 than that of the waters which origi- 

 nally brought up the gold and silver 

 from lower levels. 



(See Spurr, J. E., and Garrey, G. H., 

 Economic geology of the Georgetown 

 quadrangle. Colo.: U. S. Geol. Survey 

 Prof. Paper 03, 1908; Bastin, E. S., 

 and Hill. J. M., Economic geology of 

 Gilpin County and adjacent parts of 

 Clear Creek and Boulder counties, 

 Colo. : U. S. Geol. Survey Prof. Paper 

 94, 1917.) 



