| Show IN VV StAV IRV VIO it atit rik it it ja V nv naz THE ORIGIN OF THE FINE GOLD OF SNAKE V V robert bell M E in engineering Q Q mining journal ahe HE origin of the fine gold of snake river has been a subject of much speculation for years and has entirely baffled the theories and researches of the ordinary prospector who has traced it from the mouth of the river to its very source only to find contrary to the experience of almost all other placer fields that the same uniform fi fineness n e and filmy conditions of the delicate colors prevail aia throughout one of the most plausible theor theories ie s that have been suggested touching the origin of this exten s i v e distribution of the precious m metal e t a 1 was advanced by captain N L turner a west point man who spent considerable t time i m e investigating the problem in the early eighties captain turner advanced the theory that the gold was originally held in solution by the waters of a great in brally disseminated throughout the enormous acreage of fine gravel beds through which the river now courses the geological record of the rocks left along the borders of this stream and in the lower valley by a great dam of brown columbia bia lava feet high now plainly exposed by erosion its highest level is indicated by a stretch of conformable shoreline conglomerate gravel along t the lie west side of wood t ts rw K T A F r A F 0 4 SNAKE RIVER IDAHO NEAR BALLARDS LANDING land sea or lake that occupied the snake river valley subsequent to the miocene period and that the gradual and repeated evaporation of this great body of water by subsequent lava flows resulted in the precipitation of its metallic contents generally and evenly over its basin area this theory would seem seem to account for the uniform size and quality of the golden colors so gen grand canyon below weiser offer conclusive evidence of a landlocked land locked body of water that covered the whole valley and that probably exceeded lake bonneville in depth and areal extent at some of its higher levels this great areat body of water which might 11 aptly be called calle d lake idaho for the purpose of this article was created by the closing of the 11 river near hailey at an altitude of feet at this level the waters of lake idaho must have extended along the present course of the valley from below weiser to the foot of the main range ranche and covered a distance of fully miles in length by miles in breadth and over feet deep at its deepest point this lake suffered numerous and extein extensive v variations a r i a t i 0 n s of level durin during the later tertiary periods some of the moro recent horizons are still e exposed posed at Poe pocatello atello where on either side of the portneuf Port neuf E estuary y in in plain sight from the depot well benned denned db benches e n c h e s or terraces 0 of f shoreline shore line gravel are left exposed feet high above the town and a succession of low step terraces of lake shore gravel cut by the main track of the oregon short line railway between pocatello and american falls plainly indicate the rapid recession of the lake levels of this p period arlod and ats ks final drainage and complete obliteration by the erosion of the snake river channel to its present level these varying lake levels are well established throughout the valley within a vertical range range of feet and are now represented by the beds of conglomerate gravel alternating with great hows flows of black basaltic lava of more recent date most of these conglomerate deposits are gold bearing and their sub aerial disintegration and ero son by recent stream action is doubtless responsible for the immediate source of the fine float colors now so generally crene rally distributed through the loose gravel and silt of the present river channel and its wide flat bars prior to the iric inception eption of the great floods of black lava that have filled the upper valley the shore lines and basin area of lake idaho were almost all composed of granite and pal kozole formations these fo formations were rich in placer and quartz gold as proven by the higher slopes of the present drainage basin and by bv the number of island summits of represented by thin lines of gray silt or calcareous sediment these lines of enrichment represent flood periods they are usually from a few inches to 1 foot or or more in thickness and 1 foot to 10 feet apart the intervening space all carries gold but much more sparingly subjected to microscopic examination many of the colors show rounded gounde d edges and a concave or cup shaped depression in their flat surface and quite a pro proportion portio n of them are coated with a sugary incrustation of silica or some other substance which involves the necessity of scouring them in a cleanup clean up barrel or an pan before they will unite freely with bercut mercury y under a sharp focus of the microscope all the colors show a delicate lacelike tracery of fine brown lines that suggest I 1 chemical reaction the particles were probably precipitated from their original watery solution as chloride or bromide of gold and AM 7 IL V ANOTHER VIEW ON SNAKE RIVER those formations that have been left exposed above the sombre lava floods the chemical reactions set up by this combination of conditions and events would readily account for the aqueous origin of the gold and it seems to me altogether probable that capt turners theory is correct the quality of snake river gold is high and when prop properly eriv cleaned mints for 1935 per ounce the colors are not only fine running ning from 1000 to 2000 to the cent in value but they are also blakey in shape and are washed down stream with every summer flood enriching the low shifting bars at every short band in the stream where a favorable condition for their concentration is presented bedrock is not important to the deposit deposition Jon of the values in the high banks of loose gravel that border the stream as well as in the low barehand bare and flood planes the richest values are afterward transmuted to metallic by natural process aside from the above characteristics charac characters teris ties under a powerful glass the fine particles reveal the natural yellow color and worn knotted appearance of high grade gold nuggets the only natural alloy that the government go eminent assay office at boise idaho accounts for on shipments of snake river bullion is a small amount of silver and as the fineness of the bullion after deducting deduc the silver does not nat exceed there still remains considerable room for other natural alloys which it is not unlikely may be in part made up of platinum or iridium in fact a white gray metal in im palpably fine particles but just as readily separated as the gold in panning has been noticed at several points 1 along snake river this tb is is supposed to be one or the other of the rare metals above mentioned A series of analyses of concentrates and bullion from different points along the stream are being made by the writer at the pre present e t time and should they prove to contain an appreciable preci able amount of either platinum or iri daum the fact will lend an added interest and ince incentive etive to the recovery of snake river biver fine gold an absolutely reliable method of saviri savina t the gold and the other natural advantages b of fine climate railroad transportation cheap labor power and ground are indu inducements C eme t that should make this an attractive field for investigation and investment |
