Show 0 HISTORY AND GEOLOGY OF MONTANA J C G W miller M E in butte miner butte is probably one of the most interesting mining camps in the world the city is itself a pleasant one and exceptionally so tor for a mining camp no other camp in the Ili history story of mining has attracted more well merited attention and rewarded both capital and labor more munificently and with greater certainty virginia city nev in years gone dy by astonished the world with ner silver and gold bonanzas cripple creek colo for some years past has dazzled the very eyes of creation with her shining gold lead vule vide has also supplied the nations of the earth with her inexhaustible deposits of lead silver and gold ores but to none of those can be ascribed the sublime attributes which dame nature has bestowed upon this much favored region the most bountiful contributor of metallic wealth on the american continent if not indeed the greatest in the history of the world history the history of butte may be said to have begun in the early sixties with the discovery of gold in the gulch and in the placer beds above and in the vicinity ot of rocker hooker or in the alluvia alluvium um of the ancient lake beds which we shall call the lake bed placers As has been the case with most of the important mining camps of the west butte was therefore originally a placer camp the bold outcrop of the numerous mineral veins throughout the district became more attractive to the early miners as the limited supply of water became more scant for working their placers until finally a mining camp had sprung up and quartz mining became the most profitable industry of the district shipments of rich silver ores to salt lake smelters shelters sm elters soon attracted capitalists to this r region e g on in 1877 the walker brothers purchased the alice mine subsequent development of this property proved so prof profitable fable that in a short time the town of waler wal or er ville was wa s built up by the miners employed employ edn it the next impetus the camp received was the purchase of the lexington mine by a french com company P any for this was again augmented by the erection of more mills which after careful experiment successfully cess fully treated all silver ores to their full capacity silver producing camp with the advent of a railroad in 1881 butte had attained a high rank as a silver producer A host of other mines had come into prominence the most important of these these being the blue bird situated in the extreme west end of the district or in the vicinity of the placer fields this mine was opened op i ened in 1885 and its ninety stamp mill had produced up to 1892 about ounces of silver not until the erection of a plant by the colorado smelting smelling Sm elting company in 1879 for mak aa ap ax 1 0 u LAKEBE X HYUI TU X 13 ED N T ing copper matte or regulus can copper mining be said to have successfully begun or the copper industry established on a permanent basis in the following year the parrot and colusa calusa smelter sm elters s were built enormous bodies of rich copper ores were struck below the zone of oxidation in the anaconda and other mines which were previously worked for silver ores occurring in the gossan above the water level these copper ores were successfully treated by the various smelters shelters sm elters at immense profit and an dit it may now be said that one of the most potent phases of buttes history had begun destined to triumph with the new era of of prosperity this district has long since outrivaled out rivaled all other copper producing regions on earth interesting figures according to mr G W tower and F S emmons of the united states geological survey up to the close of the year 1896 the butte mines had produced wor worth t h of copper silver and gold As the annual product since has averaged about it is safe to place the total product of this camp to date in round numbers at about of this amount 74 per centis copper 23 per cent silver and 3 per cent gold or copper silver and gold i in addition to this it is variously estimated that the placers of west butte has yielded between and in gold the greater part of which was wa s won by the early day miners general geology Y in order to give a better general idea of the different geological formations in the butte district two plates are herewith shown plate I 1 exhibits an ideal geological section taken longitudinally through the district and a transverse north south section after F S emmons and G W tower taken through the copper bearing zone plate 2 exhibits the areal geology and general course of veins at the surface and shows the surface formations format ioni through which the veins transverse on referring to plate 2 it will be observed that the geological horizon embraces besides the vein system and lake beds four distinct kind of rocks viz true granite ap lite rhyolite and quartz porphyry all of which may ne de classed as of eruptive origin that the granites goranites gra are eruptive and of post age is manifest from the met influences of these older rocks than the later sedimentary deas at ai points of contact dark clark and dense limestone being altered to white coarsely crystallized crystal lined marwe mardie the es being baked to hard brittle siliceous slates the coarse and even granite mass snows that the liquid rock undoubtedly cooled under a cover these evidences have been noted in adjoining localities by weed emmons and tower where the sedimentary beds were observed in conjunction with the underlying granite formation a highly fine grained intrusive granite rock occurs in great abundance in the western half of the district it is composed of alkaline feldspar a little plagioclase much quartz and a little mica the occurs intrusively in the granite in a great variety of forms it also forms vast and irregular sheets of various thickness overlying the granites goranites gra more generally in the western part of the district leit is exceedingly rare in the eastern half the relation of this rock to mineral veins is the same as that of the regular granite quartz porphyry is more intimately associated with the copper bearing veins it occurs in dykes in the eastern part of the district some of which are over feet wide rhyolite occurs in north south dykes in fillings of volcanic rocks or conduits and extrusive lava flows consisting of brec cias clas and other products of explosive volcanoes and overflowing dykes this rock covers about one fifth of the area of the district the center of ihyo rhyolite lite eruption appears to have been big butte see maps which is evidently an extinct volcano to this center the many dykes are in most cases traceable the rhyolite area is centrally situated it trends in a northwest direction and forms the broken hills northwest of the district formation of ores the commonest of minerals forming the ores of the butte mines are pyrite chal pyrite coperite co galena rod onite the rarer niffie miners rs are argentite native silver native gold the oxidation products are hematite limonite cuprite native copper chryso collo malachite azurite chaleant hite and wad the earthly minerals are calcite cyb gypsum barite clorite and seri cne silica occurs also forming a large part of the gangue material of the metallic ores and as a predominant constituent of the various country rocks Go logical conclusions observations of the butte district have established or revealed the following first the fundamental granites goranites gra of the district were erupted in a vic vicious iou or plastic state and they are of post cretaceous age second that the is of later origin and perhaps contemporaneous with the quartz porphyries since it intrudes the granite third the quartz porphyries were previous to the filling of the vein fissures since the former are cut by the latter fourth the rhyolite outburst was subsequent to the opening and filling of the mineral veins since the vein system on being followed until it meets this formation becomes shattered split up and in a measure de mineralized fifth the rhyolite eruptive rocks are of miocene age since remains of that age have been found in the volcanic aan of adjoining lake beds sixth the rocky mountain uplift three miles to the east of butte was contemporaneous with the rhyolite eruption and consequently subsequent in most part to the butte ore deposits or district which was separated from the main uplift by faulting seventh the general course of vein fissures is approximately east west they are true fissures of the shear zone type generally parallel and of two kinds viz copper bearing and silver gold bearing see plate 2 Genetic genetically aily the copper veins preceded the silver gold veins eighth the vein system continues on its course comparatively uninterrupted except by local faulting and the effect of pressure it evidences clean cut fissuring some or oi which are upwards of one hundred feet in width this condition continues until they meet the upheaval to the west and the rocky mountain uplift on the east where they become shattered destroyed and mineralized de in a great measure ninth the fissure vein system developed as a result con consequent sequent to the cooling and contracting granite magna tenth from the foregoing the following conclusions is deduced after the fundamental granites goranites gra had cooled sufficiently they began to crack the first fractures were in directions approximately that of the subsequently formed vein fissures these became quartz porphyry dykes after a long lon period for refrigeration and consequent contraction of the granite magna a parallel series of east west fractures or master fissures were developed these enormous rents of the earths crust were not limited to three or four miles but the organic movement was widespread and extended to indefinite distances in either direction and reached far east of butte into what is now the rocky mountain uplift and far west into the country which afterwards was up heaved and now forms the low range of mountains seven miles west of butte the development of the fissure system was intermittent and of long duration the fissures were subsequently filled with metallic ores some with copper ores others with sil ver gold ores see plate 2 they were mineralized by means of circulating waters carrying the metals in solution the li minerals were deposited in an some instances by precipitation in others by replacement or by by this latter process of mineral deposition replacement a very narrow fissure rent may become transformed into a very large ore repository tory a hundred feet or more in width this process is that of substitution or mutual exchange of the metallic minerals held in the waters which circulate thorough the cavity for particles of the wall rock the process of precipitation leaves behind it the easily recognized characteristic of the typical true fissure vein i 1 e ore arranged in banded or rib boned structure selvage well defined walls etc tho the distinguishing features of ore deposits formed by are also easily recognized in that the ore of the deposit is quite compact the walls possess no well defined outlines and the ore often penetrates either wait wail min eral izing it for many feet from the main ore bouy 1 T f earth was disturbed the copper bearing veins in most parts have been filled meta somatically while some of the silver veins show evidence of true fissure fillings but the larger or wider ones in either case were former forme generally by replacement thus we may suppose that the early dynamic forces and agencies of nature had completed their work both morphologically pho logically and genetically and that the now much contorted vein fissure system tra this district existed then in a state of symmetrical undisturbed by igneous convulsions and the great and destructive tive terrestrial forces which operated so effectively in after ages to their obliteration through vast areas this immense parallel vein fissure system stretched out in almost straight lines and flourished for ages in a comparative state of primitive homogeneity until finally this early state or ol repose was challenged by the elements the granites goranites gra were robbed of their sedimentary beds of disintegration and subsequent erosion the great vein fissures were shattered to smithereens throughout large areas to the east of butte in consequence of the rocky mountain uplift and then perhaps at a L ime me contemporaneous with this there developed at an interval of about two miles west of the east shattered area a subterranean disturbance which must have shook the earth to its foundation the granites goranites gra were rent in north south directions rhyolite lava belched forth from the throats of volcanoes and the numerous open dykes overflowed with the same kind of molten material covering with rhyolite brec breccia cla and shattering the fissure system through a trang transverse verse zone fully two miles wide adjoining this volcanic belt and for fully four miles west or until the low range of mountains west of browns gulch is met the country is comparatively level and snows no evidence of subterranean disturbance such as would shatter or destroy the vein fissure system on its westerly course for the sake of convenience this area of country will be he hereafter reatter referred to as the west transverses trans veres zone of the butte ui district strict ane volcanic belt as the middle transverse zone and the area east of this extending to silver bow creek a as we east transverse zone zone of Dis district dietric the east transverse zone is limited on the east by the great fault plane which was developed during the rocky mountain uplift it extends nearly north south along silver bow valley and no mines of importance have ever been found in the broken country east of this fault it is limited on the west by the volcanic belt just referred to and itji it is a little over two miles wide aee platz plate 2 this zone with the exception 0 of 1 a small amount of faulting has remained ever since the formation of its ore deposits comparatively undisturbed by the dynamic forces and it comprehends every copper mine and with few exceptions ISO also every important silver gold mine dincov discovered r d so far in the district as a consequence the middle zone has already been referred to as a disturbing element it is about two and one half miles wide and comprises ses a host of silver gold mines these occur invariably in the granite and formations in spots only where the veins have escaped obliteration by the eruptive forces the vein system of this zone is as might be expected much contorted faulted and split up A few mines however ot this zone such as the blue bird nettie avonia cravonia Tr germania etc have produced considerable silver and gold the west zone so far as lode mining goes has remained wholly unexplored it borders on the higher ground or volcanic belt to the east and extends west to the mountains a distance of perhaps four miles its general aspect is that of a sagebrush sage brush desert it is in fact an ancient lake bed the slope of the marginal granite rim rock suggests that these beds are perhaps from to feet deep and that the whole area is by a type of granite rock which is identical in every respect to ix that of the east zone and also that this formation has escaped the destructive influences of the dynamic forces and hence the chances ot of discovery of an undisturbed continuation of the vein system of the east zone beneath the lake bed is highly probable and indeed should future exploration of these fundamental granites goranites gra reveal ore deposits duplicating those of the east zone no great surprise should be created lc is moreover worthy of remark if as advocated by many very eminent geologists the rhyolite eruptive rocks of the middle zone have influenced fluen ced and augmented a secondary deposition of ores on the east side it is far from |