232 GEOLOGICAL SURVEY OF THE TERRITORIES. 



believe that the data regarding development, with depth of the mines, 

 must necessarily afford much information on the distribution and for- 

 mation of ore-bearing veins in general. 



OCCURRENCE OF LODES. 



Two systems, chiefly of lodes, are found, the one striking approxi- 

 mately northeast to southwest, the other northwest to southeast ; and 

 the two directions may be observed to occur at the same places, produc- 

 ing a crossing of the veins. 



At all points, where none but the volcanic rocks crop out, the veins 

 run through them in a very regular course, showing but few deviations 

 from the straight line. Often quartz veins, containing but little ore., 

 were observed from our high stations some distance off, keeping a regu- 

 lar course at times for more than a mile. As the quartz is harder than 

 the surrounding rock, it stands out prominently, while the former, imme- 

 diately adjacent, is weathered off. Decomposing pyrite imparts a brown 

 color to the projecting ledge. As a rule, the walls may be pronounced 

 well defined, although near the surface atmospheric influences would 

 have the tendency to render them less so. Frequently the veins can be 

 seen along the face of a rocky hill for several thousand feet. This was 

 the case on a mountain opposite Howardsville, where a number of veins, 

 some of them claimed, are visible for a vertical distance of more than 

 2,000 feet. The accompanying cut will illustrate their position. From 

 the north side of the summit five parallel veins traverse the trachytic 

 rock for a vertical distance of 1,200 to 1,400 feet, and are in their turn 

 cut by a large vein starting from the southern side, the "Mammoth lode." 

 Farther to the south, beyond the last named, there are several smaller 

 veins, having an almost vertical dip. Debris covers the lower portion of 

 the veins, hiding them out of sight. In Cunningham Gulch the lodes, after 

 first running through the metamorphic rock at right angles to its strike, 

 enter without apparent disturbance or dislocation the horizontally strati- 

 fied volcanic cap. At the shallow depths which have thus far been 

 reached, no change in the character of the ore could be observed. The 

 stratification in Arastra Gulch is not so well marked/the rocks show- 

 ing a more massive structure, although a few miles beyond its head 

 they are regular again in their occurrence. Numerous other lodes- al- 

 ready located occur in the volcanic rocks. The strike approximates to 

 that above indicated. No definite relation, however, of their course to 

 the structure of the rocks containing them could be observed. 



MineraJogically 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, showing 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.'McIntyre, all from 

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

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



