200 KANSAS CITY REVIEW OF SCIENCE. 



portions of the North Park He along its eastern limit and just here there have 

 been many mines opened within the past two years. 



The line of junction of the Archean (granite, gneiss and mica schist) rocks 

 with the volcanic {rhyolites and trachytic porphyries) rocks is about north and 

 south, and near this junction are occasionally seen dolerytic dykes, whose strike 

 is also north and south. The principal veins also extend in a north and south 

 line parallel with the strike of these rocks, and they are nearly everywhere ore- 

 bearing, and in some places rich in silver ore. The minerals in these veins as 

 found may include : Sulphuret of silver ; Ruby silver and other silver ores ; • 

 Copper and iron pyrites \ Oxide of copper and of iron. 



Complete analysis may result in the discovery of other interesting ores and 

 minerals. Calcite, Dolomite, Fluorite and Quartz are found at most of the mines. 

 The veins vary from one foot to twenty feet in width, but those worked on are 

 generally from two to five feet wide. 



Passing up Jack's Creek from Teller, we find at Teller a dark trachytic por- 

 phyry traversed by doleryte dykes, having a north and south strike, but dipping 

 to the west at an angle of 60 degrees. Similar rocks are found as we pass up the 

 creek for three miles generally presenting the general appearance of metamorphic 

 porphyries, but some have a decided schistose character. Beautifully banded 

 and contorted gray gneiss is found a little way up from Teller. 



At the " Gaslight " mine work was done on a coarse, gray porphyry twenty- 

 five feet wide. Porphyry walls appear on the west with dolerite on the east. 

 The gangue rock shows quartz in drusy cavities, with sulphuret of iron dissemin- 

 ated in the veinstone of quartzose rock. Both calcite and dolomite occur here 

 in crystals. 



The adjacent porphyry here is a gray with rather large light gray crystals. 

 This mine was discovered in June, 1879, by Jno. and A. Lefevre, formerly from 

 Missouri. It was the first mine struck on Jack's Creek and when sixteen feet 

 down was sold for $20,000. In 1882 it was again sold when sixty-five feet down 

 at quite an advance. 



Above the " Gaslight" dolerite extends for a mile or more to the^Pennsyl- 

 vania mine, and the New El Dorado. At the "Yellow Jacket" mine the work 

 was prosecuted on dolerite with poor success. White and green fluor and pyrites 

 occur on the wall rock. At the " Pennsylvania " mine at forks of Jack's Creek, the 

 walls are still dolerytic, with streaks of pyrites, carbonate and fluorate of lime and 

 quartz and some silver. 



The next mine, just above the last, is the "New El Dorado." It lies directly 

 on line of contact of the volcanic rhyolites and dolerites with the gneissoid 'and 

 schistose rocks. The vein, four and one-half feet wide, bears north and south, 

 dipping a very little to the east and with ore well disseminated in quartz, j [Its 

 east wall is dolerite, the west is quartz. Some galena has been obtained^here. 



The " Constellation " due north of the last and across Jack's Creek, high up 

 the mountain, is supposed to be a continuation of the New El Dorado. The rocks. 



