| Show formation and geology without going into the subject technically in describing the formation of stateline Stat eline district it may be said that the ore bodies make in contacts and fissures in in a great porphyry belt of considerable width and breaking through the country in a northerly and southerly direction in our souvenir geological number of Dece december niber last judge grant H smith contributed an article on the geology of stateline Stat eline that is so exhaustive and interesting 6 in the treatment of this subject that we reproduce it almost in its entirety mr smith says ge geology and formation stateline Stat Sta eline teIne range is one of the most ex bentive of the many small mountain ranges which corrugate the surface of western utah and nevada the trend of these ranges is northerly and southerly and the formation is usually of igneous origin to the north and south of stateline Stat eline the mountains are precipitous and craggy but within the mapped area they have been much worn down by the elements stateline Stat eline range is composed of eruptive rocks and seems to lie along and cover what was once a long wide and deep seated fissure from which a vast amount of liquid rock flowed east and west building up a wide expanse of country and finally forming the mountain range like a huge dyke the early flows were of andesite tubs tuffs and breccia later came the quartz porphyry which forms the core coe of the range and which probably lifted the earlier formation into a structure like the henry mountains within the mapped area of the dome the has been eroded leaving a large irregular hilly basin and exposing an irregular belt of quartz porphyry or rhyolite nearly a mile wide and two miles long the porphyry is again exposed about ten miles bailes north of stateline Stat eline where the confidence and perseverance mines are located and reappears several miles to the south where the promising mines of deer lodge and pikes diggings are found there were several intrusions of porphyry each somewhat different in texture and composition which made in parallel belts as it formed by the reopening of the great eruptive fissure the early eruptive rocks are not mineralized the quartz veins are all aund in the porphyry the main body of porphyry i is hard bard and iron stained ind reddish or purplish in color it covers the central portion of the mapped area and n the quartz veins of this porphyry gold values greatly predominate the other small b be e ts As of porphyry which lie to the west of the main belt are lighter in color looser in texture and more felde and the veins therein are largely silver bearing the utah spur little giant ophir burro venus high line and hope veins are in the silver bet belt while the other veins shown on the map are largely gold bearing the country rock is similar to the for fo mation in which the mines of bodie cal were found and is not unlike the comstock and tonopah porphyries ries ribs and cliffs of porphyry standing above the main porphyry mass and tending northerly and southerly are a feature of the landscape these are locally known as dykes they are not separate intrusions but have resisted erosion by reason of superior hardness which is due to a high percentage of silica these dykes are usually accompanied by quartz veins which accounts for the silica veins and ores the porphyries ries were extensively fissured and the fissures have been filled with quartz the main lines of fracture extend northerly and southerly and nearly all of the quartz veins in the district have been formed in gokh north and south fissures the notable exception to the rule of northerly and southerly veins is the big east and west veins upon which the three principal mines of the district are located viz the johnny the margaret and the ophir many of the small veins and stringers of quartz occupy coo cooling ing cracks and shallow fissures of the porphyry and these sometimes contain rich ore the larger veins are quartz filled fissures that seem to have been opened by great pressure from below acting upon the porphyry mass after it had solidified these veins are persistent and deep seated and may be depended upon the principal ore bearing veins maintain a fairly uniform width of from three to six feet at times and particularly in the ore shoots they widen to ten or more feet there has been comparatively little faulting of veins when it occurs the faulting seems to be due to a later intrusion of porphyry As ad a rule the silver bearing veins lie between porphyry contacts and the gold bearing veins in the iron stained porphyry the north and south veins commonly dip to the west at an angle of from 50 to 70 degrees the east and west vein dips to the north at an angle of 65 degrees the droppings crop pings and explored portions of the principal ore bearing veins of the district are indicated on the map by dotted lines the country rock is frequently covered with wash and debris under which the veins disappear di appear from sight but they almost invariably reappear on the next high ground the veins occur in well defined systems or zones as a glance at the map will show the principal veins may be grouped into four zones or vein systems as follows utah spur little giant burro and venus big 14 willowvale willowdale Willow vale crown point and free coinage jumbo gold delt belt and utica and johnny margaret and ophir it is probable that the creole vein belongs to the last named systems and the utah spur seems to be the extension of the ophir vein which has swung sharply to the north the country rock along these zones is much sheared and fissured several parallel veins lie very close together and it has not been possible to indicate them all on the map the walls of the veins are generally gena rally well defined but at times the ore is a replacement of porphyry and gradually fades into the wall reck rcck as the ore deposits at ai cripple creek often do the vein filling is white grayish or reddish quartz together with shattered quartz and porphyry and some clay which usually lies along the walls fragments Frag meats of country rock somewhat decomposed and are often found enclosed within the quartz very rich ore sometimes makes about these fragments indicating di that they have been conducive to mineral deposition the veins often contain considerable flour spar which seldom contains gold or silver in paying quantities black oxide of manganese is found in nearly all of the veins and occurs in greatest abundance in the ore shoots the iron is rarely found in sulphide form the ore is generally hard close grained quartz stained with iron and manganese the richer portions showing in dark colored spots and bands there is considerable evidence of crushing and se sei conary enrichment the ores greatly resemble in character those of bodie cal of the comstock lode and of tonopah To ores found in this char acter of porphyry throughout the west usually have the same characteristics and are undoubtedly derived from the body of igneous rock at greater depth the ore usually occurs in well defined and continuous shoots in the johnny margaret ophir vein the shoots rake into the west at an angle of about 45 degrees and occur at or near intersections with north and south veins another noticeable feature of this vein is the fact that in the johnny ground the gold values largely predominate in the margaret the gold and the silver values are about equal while in the silver values are largely in excess the ores 0 the district except those found in the silver veins are what are generally described as free milling the only metallic contents being gold silver a small percentage of iron in various forms and some manganese As a rule they are low grade averaging from 5 to 20 per ton very rich samples may be taken from almost any vein and considerable ore has been shipped that netted from 1000 to a car but high grade ore in quantity is not common in the future everything will be milled 0 bithe ground |
