24 BULLETLV 12, UNITED STATES NATIONAL MUSEUM. 



(3) Yarioiia sulphides, especially galena, in quartz aud rbodochrosite. Ordinary 

 run of ore. Moulton Mine, Deer Lodge County, Montana. (55575.) 



(4) Pyrargyrite and stepbanite, in quartz. Rich ore. Grove's Mine, Reese River 

 district, Lauder County, Nevada. (15127.) 



(5) Pyrargyrite and stephanite, in quartz, vrith various other sulphides, especially 

 pyrite. Rich ore. The specimen sliows the full width of the vein. Dollarhide 

 Mine, Reese River district, Lauder County, Nevada. (15136.) 



THE ONTARIO MINE. 



This mine is situated at Park City, Summit County, Utah, and is one 

 of the model silver mines of the country, having been a constant pro- 

 ducer of bullion since it was first opened in 1874, and being now well 

 developed and prospected several years ahead of the actual mining. 



The vein is a contact between a porphyry hanging wall and a 

 quartzite foot wall, the latter dipping towards the vein. The vein 

 proper is 10 to 45 feet thick, while the pay streak varies from 10 inches 

 to 16 feet. It has been developed for a distance of 3,000 feet along the 

 strike and to a depth of 1,000 feet. There are three three compartment 

 shafts, two compartments being for the hoisting of ore and the other for 

 l^umps and pipes. Owing to the shattered and fissured nature of the 

 foot wall the mine receives the drainage of a very large area, and is con- 

 sequently very wet ; 0,000 gallons a minute of water are pumoed and 

 drained from it. 



The ore from the upper levels was free-milling, but as depth was 

 gained it became more and more base from the increase of zinc, lead, 

 and copper sulphide minerals, and all the ore required roasting with 

 salt. At still greater depths galena, very rich in silver, appeared 

 abundantly, and now considerable smelting ore is produced. Thus the 

 mhje furnishes an excellent illustration of the changes which take place 

 in going down upon a vein. 



The ore consists of quartz and sulphides, most of which are more or 

 less decomposed ; pyrargyrite, galena, blende, tetrahedrite, and car- 

 bonates of copper being readily discernable, while wulfeuite and free 

 sulphur are occasionally found. There is a considerable amount of 

 clay, generally more or less stained by copper. 



The collection from this mine was made by Captain Keith in October, 

 1884. It includes nineteen characteristic specimens taken over a large 

 area of the mine, and is thoroughly representative. 



The following specimen represents the general character of the vein: 



(1) Galena, blende, tetrahedrite, pyrite, decomposition products. From 4th level, 

 670 feet west of drain tunnel. (55733.) 



Five samples from different points on the fifth level west of drain 

 tunnel show : 



(1) Quartz, colored by various decomposition products, especially copper. 1*25 feet, 

 (55726.) 



(2) Decomposition products, in quartz. 400 feet. (.55729.) 



