290 GEOLOGICAL SURVEY OF THE TERRITORIES. 



A southeasterly dip of about 15^ to 20° is noticeable. The thickness 

 of the vein between walls varies from 6 to 10 feet along its line of 

 exposure as well as going down deeper. Galena, mostly of the fine- 

 grained variety, forms a large body of ore in the vein, associated with 

 sphalerite and some pyrite, while the gangue-rock is made up of quartz, 

 with a small amount of calcite. At this point, the sulphuret of cadmium, 

 greenockite, was found iu a specimen of sphalerite, which had been 

 thrown out on the dump several years since. In no other mine or other 

 dump was this mineral found, although search was made for it. Besides 

 the minerals mentioned above as occurring, there is chalcopyrite and 

 cerussite. 



The Eunning lode is the last one of these galena lodes, and is situated 

 on Eunning Hill, southwest of Black Hawk. Its course, is almost due 

 east to west, with a vertical dip. For 700 feet the vein has been traced 

 and partially worked, reaching a depth of about 100 feet. Single 

 streams of galenite are distributed throughout the vein, (Plate IV,) 

 running parallel to its walls, but toward the west they seem to consoli- 

 date into one mass, forming a galena-vein 14 to 15 inches in thickness. 

 Sphalerite occurs quite abundantly ; less so pyrite and chalcopyrite, 

 which are both found in thin seams, or dispersed throughout the 

 gangue-rock. This latter is composed mainly of quartz, with some feld- 

 spar and magnesite. 



These four lodes are perfectly isolated in their character as well as in 

 their position from all the others, and, although they show but little 

 deviation from the ordinary strike and dip of the others, their occur- 

 rence seems out of the regular order of things. In explanation, if one 

 were desired, the view might be offered that, provided heat was ever 

 one of the agents in forming those lodes, those metals requiring a lesser 

 temperature for volatilization are now found to be removed farthest 

 from the center of the vein-system. 



Another lode that has become famous for its production in quantity 

 of a mineral thus far regarded as a rare species is the Wood lode, sit- 

 uated to the north of the creek in Leavenworth Gulch, also outside of 

 the regular vein-circle. With both walls of granite, it strikes about 

 east 3^ north. When I visited it, the shaft was full of water, and it 

 was impossible to get access. Besides producing the unparalleled yield 

 of pitchblende, it is said to pay well in gold ; but as I have no reliable 

 data with reference to the mine at all beyond the fact that it contained 

 and probably still contains pitchblende, it may be justifiable to stop 

 here. 



It remains to be said, with reference to the minerals found in and 

 belonging to the various lodes, that, almost without exception, pro- 

 ducts of decomposition may be collected on the dumps; for instance, 

 pseudomorphs of limonite after pyrite, sulphates of iron, copper, and 

 zinc, and others. A portion of the soluble sulphates is carried off by the 

 waters washing down the hills, and transferred thereby into Clear Creek, 

 which carries them in solution for a long time, and evidently does not 

 deposit them until it reaches the plains. I have observed that if some 

 of the deposit of Clear Creek was taken at Fisher's ranch, which is 

 only five miles from Denver, and rubbed on a bright iron or steel knife- 

 blade, after having been slightly moistened, metallic copper would at 

 once be deposited on the blade, owing to the sulphate of copper, which 

 had been carried down for about forty miles and deposited at that point. 



After having examined the greater portion of the main lodes of this 

 district with a view to determining their correlation as well as their 

 persistency, the deduction seems justifiable, based upon the observed 



