158 



observed. The stratification in Arastra Gulch is not so well marked, 

 the rocks showing a more massive structure, although a few miles be- 

 yond its head they are regular again in their occurrence. Numerous 

 other lodes already located occur in the volcanic rocks. The strike ap- 

 proximates to that above indicated. No definite relation, however, of 

 their course to the structure of the rocks containing them could be ob- 

 served. 



Mineralogically speaking the veins belong altogether to one system, 

 with the exception of a few in Arastra and in Boulder Gulches, of which 

 mention will be made hereafter. Minerals of a relatively low degree of 

 volatilization form the main bulk of the ore, others, however, not being 

 wanting. 



The persistency of the veins in a vertical direction is a matter of im- 

 portance, where nothing can be learned by the study of artificial depths. 

 It appears to me that it may be regarded as a rule that wherever 

 debris or some other similar cause does not obscure the view of the out- 

 cropping vein, that vein extends to considerable depths. About seventy- 

 five lodes were located on Mineral Point, showiug very promising ore 

 from the surface downward. Sufficient work to retain the claim had 

 been expended upon quite a number of them. Several gentlemen, G. 

 W. Kingsbury, J. E. Hanson, A. W. Burrows, C. H. Mclntyre, all from 

 Yankton, Dacotah Territory, and W. H. Van Gieson, P. Houghton, 

 and S. H. Tuttle, from Whitewater, Wisconsin, were continuing the 

 prospecting as well as the further developments of the veins already 

 claimed. On Miueral Point the main strike is northwest to southeast 

 approximately, although several lodes cross each other, and others 

 occur, striking from northeast to southwest. As a rule, the width be- 

 tween walls may be stated at 4 to 12 feet, but larger veins occur. The 

 ores mainly found are galenite, middle to fiue-graiued, containing 

 silver, sphalerite, from light yellow translucent to the brown varieties, 

 pyrite, chalcopyrite, and fahlerz, (brittle silver,) which throughout that 

 region appears to be an antimouial tetrahedrite, containing mainly sul- 

 phur, antimony, copper, and silver, replacements being produced by 

 iron and zinc. About 8 to 13 per cent, of silver may be regarded as the 

 limits within which it occurs in the pure mineral. This variety of 

 tetrahedrite has been distinguished as freibergite. 



The gangue appears to be mainly quartz. As some of tbe locations 

 of that section, belonging to Eureka district, I would mention Dakota, 

 Mineral Point, Red Cloud, Little Twinkle, Mastodon, Bond Mine, and 

 Equator. One of the lodes on Mineral Point shows a manganese de- 

 posite on the surface, (psilomelane,) while farther down galenite forms 

 the main body of the ore. 



In the Placier Gulch, Burrow's Park, Adam's Park, and at the head- 

 waters of the Uncompahgre a number of lodes have also been located, 

 showing ores similar to those from Mineral Point and the immediate 

 vicinity. 



Upon the mines of Eureka Gulch no date could be obtained, owing to 

 a lack of time. 



Descending Cunningham Gulch, Galena Mountain is found on the right 

 hand, while Kendall Mountain is on the left. Near the head of the gulch 

 and on either side lodes have been located, and worked to some extent. 

 As above mentioned, the lower portions of the caQon consist of chloritic 

 schist, stratified, but standingon edge ; while the upper portions are formed 

 by the bluish volcanic rocks of No. 4. Several well-defined veins extend 

 from the lower to the upper, and, as I was iiiformed, the continuation 

 had in two instances been traced beyond the ridge of the mountain to 



