282 GEOLOGICAL SUSVEY OF THE TERRITORIES. 



The well-known crystals of ortboclase, both simple and Carlsbad twins, 

 from Gregory Hill are contained in the porphyry that forms its summit. 

 On Bobtail Hill it has a greenish to maroon color, containing smaller 

 crystals of ortboclase and numerous small crystals of pyrite. At the 

 dike, on Eunning, it is more compact, of a brown color, containing, in 

 the microcrystalline paste, very small particles of hornblende. Differ- 

 ent from these is that on Procer, very compact, Vv^ith a large percentage 

 of quartz -5 it has a light-yellow to flesh-colored tint. 



The gneiss of the entire region is of one type, although numerous 

 varieties occur. Mostly it is finely laminated, of a bluish color when 

 fresh, brown when decomposed. Black mica accumulates at some 

 points, changing its charaeter into that of a mica-schist. ITeither in any 

 of the gneiss or the granite is magnetite wanting. With reference to 

 the relation of lodes to these formations, it may be said that they are 

 extremely simple, being contained either in the gneiss or the granite, 

 if not forming contact-veins between these two, and again found 

 between granite and porphyry. Quite a number of them are contact- 

 veins— sometimes only for a xjortion of their entire length, as, for instance, 

 the Bates. Earely can the fact of their being contact- veins be deter- 

 mined on the surface, only a few cases having been observed in which it 

 could be done ; but, l)y carefully observing the walls of a lode, the re- 

 spective formations to which either one belongs could mostly be ascer- 

 tained. Upon the strike or dip of the lodes, these various circumstances 

 seem to have had little or no eifect ; neither have they, within certain 

 limits, changed the character of the ore. Although it might seem 

 possible or even probable, the porphyritic eruptions have produced 

 no noticeable change in the lodes of their vicinity, unless it might be 

 regarded as an effect of this kind that those lodes found in immediate 

 proximity to the porphyries generally yield lower returns in bullion than 

 others farther off. 



Two main systems of lodes are found here, those belonging to the one 

 striking almost due east and west, the others about northeast to south- 

 west. Of the two, the former are the most numerous ; to the latter 

 belong the Fisk, Gregory, Bates, Leavitt, Prize, and a few small lodes. 

 No distinctions from a mineralog-ical point of view can be made, neither 

 is there any constancy noticeable in the mode of occurrence of these 

 veins. Contrary to my expectations, the mineralogical character of the 

 ores was found to be a very uniform one, showing little variation in> the 

 number and species of minerals composing them. But one interesting 

 fact was observed, that in the more or less central portions of that 

 mining district the lodes showed but very little blende and galenite — 

 mostly pyrite and chalcopyrite. If an elliptic line is drawn, inclosing 

 just witMn it all the principal mines of this section, it will be found that 

 the J. P. Whitney, the Forks, Eunning, and Dallas are nearest or on 

 that elliptic line, and these lodes are all worked for lead and silver, con- 

 taining galena and blende as their principal ores. A limited number 

 of workable gold-mines are situated outside of this circle yet, but those 

 upon which the mining enterprise is chiefly based are within. 



Disturbances — dislocations — are very rarely found iu the lodes of this 

 region ; scarcely even any material deviations from the dip.* Only a few 

 of the lodes slope over 10*^ ; as a rule they are very nearly or quite ver- 

 tical. Eamifications occur quite frequently, more so toward the west 

 end of the lode than at the east — a feature which was observed in a con- 



*A deflection from the usual course takes place on the eastern slope of Gunnell Hill, 

 •where a dike of garnet and epidote rock crosses it, in consequence of which three or 

 four small veins near it were formed that have a course about north 10° east. 



