178 



GEOLOGICAL SURVEY OF THE TERRITORIES. 



Fig. 20. 



The dike is in the same mountain, not more than three hundred yards 

 from the Gregory lode. It is exposed by an artificial cut for a road up 



the side of the mountain, and but for 

 this circumstance would not have 

 been visible from the surface. It is 

 vertical, twenty feet high, and three 

 to four feet wide. The materials in- 

 closed in the dike are evidently very 

 old basalt, yellow buff color, with 

 cavities filled with decomposed feld- 

 spar. The country rock does not ap- 

 pear to have suffered changes, but the 

 lines of bedding are entirely inter- 

 rupted, and curved upward. 



The following notes on the Sweet- 

 water Mines were taken by Mr. Ar- 

 thur L. Ford, the mineralogist of the 

 expedition : 



Cariso Mines. — Worked by Mr. 



Dyke, 



near Central City, 



COLORADO. 



Eoberts, of South Pass City. Shaft 



one hundred and forty feet deep, sunk in vein of very refractory quartz - 

 ite averaging four and one-half feet in thickness ; strike of vein north- 

 west and southeast, with dip of 70° to northeast. Cap rock and wall 

 rock consist of tough gneissoid slate containing a little free gold, and 

 occasionally showing a few small cubes of iron pyrites. The gold con- 

 taining the quartz is very finely disseminated, but is " free " and very 

 pure, and hence easily amalgamated ; it contains about one-half ounce of 

 silver. About four tons of ore are being taken out daily, with an average 

 yield of $75 per ton, and sometimes doubling that amount. The quartz 

 is of remarkably even quality, seldom falling much below the average 

 yield. Mr. Eoberts estimates the gold already produced to amount to 

 about $75,000. The mine makes very little water, about eight or ten 

 buckets being taken out hourly. 



Young America Mine — Mr. Incath, manager. On same lode as the 

 Cariso ; quartz contains considerable disseminated oxide of iron, but is 

 not on that account less refractory. Ore averages about $23 per ton — not 

 visited. 



East End Mine — On Miner's Delight lode, Mr. A. C. Hasey, manager. 

 Shaft sunk sixty feet, through slightly laminated, easily-worked quartz 

 of varying color, that having a clear blue tinge supposed to be the best, 

 especially if breaking easily into lamina of from one to one and one- 

 half inches in thickness. Strike of vein northwest and southeast, with 

 dip nearly perpendicular. Yein, like the Cariso, conforms with the 

 gneissoid slates which form the wall rock, and which are supplanted 

 toward the surface by a porphyritic gneiss holding small quantities of 

 gold and overlying the vein, though not forming a true cap rock. Very 

 small traces of pyrites are contained in both wall rock and quartz. All 

 gold, however, seems to be full. Seven tons per day of ore were being 

 taken out by hand labor, ore averaging $20 per ton. Gold not so pure 

 as that of Cariso, though very bright and easily amalgamated. A great 

 deal of the gold is in flakes of considerable size, especially between the 

 lamina of the quartz. The quartz is so soft that no blasting is needed. 

 A good deal of moss agate occurs in the vein, noticeable when the quartz 

 is clear. 



Miner's DeJiglit Mine — Just west of preceding; the claims join. Lode 

 *is the same, but pinches to an average width of two feet. Vein stopped 



