Show iwo im im IM I M ifa IN lei im lei IM I M lot lei 14 lei biffl lei lot loll 1011 iam ION formation of the pearl section owl robert N bell E M state inspector ol of mines for idaho describes the geology and formation of the te pearl section as follows the most important formation of the westview West view mining district is meta morph granite associated with an excessive de of ancient dyke rocks and gold bearing fissure veins that are distinctively of the true fissure type the granite formations of this district are a close modification of the great granite mass of central idaho which is the largest connected granite area in the united states the fresh rock exposed in the different deep crosscut cross cut tunnels along this mineral belt varies from very fine to very coarse grain and carries an excess of coarse and bronze colored mica and evidently a predominance of the more soluble feldspars feld spars for it crumbles and disintegrates readily and covers the surface of the hills with a deep mantle of debris producing rounded grassy slopes and gentle contours which prior to the advent of the sheep herds are said to have formed one of the finest cattle ranges in the west the low buttes and ridges immediately south of pearl culminating in prospect peak at an elevation of feet are capped with a series of unaltered sedimentary beds payette formations fully feet thick these in turn have been ruptured and overflowed by vents and dykes of rhy rhyolite oolite and basaltic lava these sedimentary beds and lava overflows were formed during tertiary times a comparatively recent geological period and contain no veins but cover up and obliterate an important section of the proven mineral bearing zone course that is one half mile wide and fully a mile long between the strike of the lincoln vein and the ari friday vein the area is very likely to contain rich ore courses but only can be proven by deep sinking through the barren formations referred to that cover the ancient vein bearing granite surface the dyke rocks that accompany the ore veins in the granite formations of the westview West view district are very numerous and some of them of large size they strike 10 to 40 degrees north of east with a steep dip to the north these dykes are composed of dark green smooth grained diorite varieties and in places are accompanied with rather coarse mottled porphyry of lighter color and contain large crystals of quartz and feldspar the veins roughly parallel the dykes in both strike and dip except in the vicinity of pearl and horse shoe bend where whery the prevailing course is about due east and west they are younger thau than the dykes as a proved by the fact that they cut through the dyke rocks in both dip and strike at several points and are usually found much disturbed and splintered up the best ore is usually found where the walls are granite commencing at the lincoln mine the mineral bearing zone extends almost due northeast for seven miles to the united mines and osborne group right down on the bank of the payette river and is fully a mile and a half wide this entire belt is blocked out solidly with continuous locations and it is safe to say that every location covers a fissure vein and some of them a series of veins containing more or less gold bearing ore the prevailing northeast course of this mineralized zone as against the predominant east and west strike of many of its included fissure is probably due to north and south faulting movements which in fact are indicated in the deeper opening of some of the mines mineralogy KINER the free oxidized surface of the west view district such as are amenable to simple mechanical separation by crushing and plate amalgamation extend to very shallow depth on the veins in no place have they been found to extend down more than feet and at several points where the fissures cross a gulch or depression and produce a spring the base sulphide ores have made their appearance within ten feet of the surface base ore however is only a relative term in the present stage of metallurgical lurg ical science and it is safe to say that any ore containing a value of 10 per ton in gold can be successfully and profitably treated by some of the various methods now in vogue the vein fillings of this district contain very little hard free quartz and like the enclosing formation are disintegrated and worn down even with the surface and consequently droppings crop pings are rarely met with with a few exceptions the development of the district so far is confined to the shallow skylight and daylight work and the smooth hillsides hill sides are spotted with hundreds of prospect holes with lebrown litt dumps arranged in definite lines and indicating the trend of the fissures the surface ores are composed of a brown oxidized iron stained gangue frequently mixed with lead carbonate which Is considered a good sign of value they carry from a trace to per ton in fine rusty gold and in some instances associated silver values have been found in the form of chloride that have yielded assays essays of several hundred ounces of silver to thod the ton toll the veins are from a foot to thirty feet fe wide and below the zone of oxidization found to contain a blue chalky feldspar are gauge well sprinkled with metallic 0 sal g aphides and almost invariably carrying a 1 well defined pay streak of high trade grade ore or e this rich ore is usually from a few inches 3 to a foot or more thick and may occur eith er on the hanging wall or on the foot wall or be split up into thin parallel seams through the mass of the vein and connected with divergent stringers in places like a coarse network the rich ore streaks are composed of a massive combination of iron pyrite zinc blend arsenical pyrite and galena they vary in value from 20 to several hundred dollars per ton and are frequently sacked and shipped without further treatment disseminated semina ted through the granular vein filling the same mineral forms mill dirt and is readily extracted to a clean concentrate on wilfley tables when the arsenical pyrite predominates the values run higher in silver and the soft yellow iron sulphides sulp hides mixed with galena are the most favorable indication di for high gold values some of the veins of this district show considerable disturbance especially when they penetrate dikes at other points considerable sid erable friction breccia is shown together with a development of considerable tale talc which makes milling difficult but when the veins are contained in straight granite walls the gangue is usually granular makes a free running pulp and is rapidly crushed and cleaned of its mineral contents by concentration tra tion the occurrence of high grade ruby silver and chloride ore at a number of places in this district is a favorable indication for future rich strikes as development progresses in depth |