Show how and where to prospect for lead mines some pertinent pointers for the field man by S F hunt mining geologist prospecting for lead is a thankless vocation that deserves good will lead ores are growing in demand and becoming scarce and difficult to obtain from a lack of prospectors to search for and disco discover ver new mines this situation arises in part from the general disregard and bad repute that crooked promoters and stock jobbing swindlers lers have succeeded in unloading on the hapless prospector with the approval of an indiscriminating public but regardless of any disfavor which attaches to metal mining in general prospecting for lead has never been patronized nor e encouraged in the west in the past when the prospector discovered lead instead of high grade gold or silver ore he was told that his lead was base ore low grade and useful as a flux only then to turn down both him and his prospect appeared to be a generous act of christian kindness that could not be neglected everybody insisted on high grade or nothing whereas real lead mines notwithstanding are characteristically lean in gold and silver content geologic relations lead deposits are of two iwo distinct and unlike types the annual production from which is about equal in amount those in the western states are mostly of the intrusive fissure vein type in the missouri mississippi valley region they are all of the blanket and bedded type these valley deposits are ranged along old shore lines encircling broad low rock domes where no intrusive porphyries ries are in evidence both types of deposits and their numerous intermediate varieties possess some distinctive earmarks and habits of occurrence not displayed by those of gold silver and copper although related in time and locality to the same manifestations of ore forming agencies As a rule copper deposits outcrop at surface as barren rusty iron iron gossins gos sans intimately connected with intrusive granite and porphyries ries gold and silver deposits outcrop usually as hard quartz veins in or near the eruptive porphyries ries or volcanic centers as at tonopah and cripple creek but lead ore does not make in the granite formations it does not show rusty iron gossins nor bold siliceous outcrops as do copper gold and silver the commercial lead deposits inhabit the limestone shale ale chert and quartzite formations not in but in in the vicinity of rocks they occur in these stratified fort nations when they have been domed faulted fissured and altered by the invasion of intrusive rocks to explain magmas hagmas and solutions are the moving agents agent I 1 in the forma formation tion of al all I 1 primary ore deposits the rock forming elements from e magmas hagmas ire re the molten which aich granite r acks acks are derived by cooling and crystallize tion are compound sulphur and arsenic solutions of the metals of ore deposits they are made thin and tenuous by heat and pressure only and exist as foreign il non in ingredients in the molten rock magmas hagmas and are held and incorporated in them only by gaseous fusion and mechanical mechanic al entanglement the term was employed by the al chemists of old in search of a universal solvent or flux of the metals in contrast to the deanin meaning 4 of magma and aqueous solution solutions are the residual waste spent end products from magmas hagmas and alike this view of volcanic action serves to explain why so many intrusive formations are barren yielding no ore deposits and why veins veins of ore are so erratic and not deposited deposit edby by ascending hot spring solutions at or near the surface ore making never reach the surface the ore making unlike the rock forming magmas hagmas never reach the surface but deposit their load of metallic sulphides sulp hides progressively b as they ascend into colder rocks by the loss of heat and pressure so in the formation of ore deposits gold copper and zinc crystallize out of a at greater depth and under more heat and pressure than does lead but silver is held in suspension even longer than lead and is deposited under less pressure in still colder rocks this may account for many silver veins changing to lead in depth whereas copper and gold veins do not from this peculiarity of deposition it is evident that lead is always deposited at intermediate depth from a cooling and therefore can become exposed at surface only by faulting and subsequent erosion erosion hence as the surface outcrop of veins of ore is the result of erosion it follows that the depth and extent of the removal of of the overlying b strata b by y denudation is one of the controlling crollin b factors as to whether a particular system of veins may carry go gold id copper zinc lead or silver I 1 at surface yet the nature and composition of the related intrusive rocks have much to do with the matter also for instance the emitted from the dark green to blacky black ultra basic granites goranites gra and peridot ites and the pink and light colored highly siliceous granites goranites gra and are all deficient in lead but yield copper gold and silver but the derived from the intermediate ves the trac hites mon di orites and sye all light brown colored lead which will migrate blue gray ray or yellow expel to some e colder bed or stratum of dolomite chert or quartzite to replace quartz veins veins in in granite sometimes contain lead mixed with other sulphides sulp hides but not in commercial ani amounts showings of lead are more numerous in lime than in quartzite and usually carry more silver but for grade and quantity the deposits in chert and quartzite are more permanent and productive many of the so called limestone deposits are replacements of inter stratified beds of chert or quartzite cracks and fissures in lime contain lead and zinc and both may replace rn agnesian dolomite the habit of silver zinc and lead to spread and bed out under a black shale cover should be remembered finally whether in lime chert or quartzite lead deposits form over and along domes doines in cracks and fissures and as saddle reefs and parallel runs and channels in shoreline shore line embay ments surface indications the surface exposures of lead deposits are not showy and pronounced the gangue angue a minerals are usually soft sandy or earthy and white gray or yellow in color these peculiarities make their outcrop inconspicuous and generally covered with an oNer overburden burden of wash or yellow clay when iron is present in the ore it commonly changes to a soft yellow ocher lead ocher still in other places the iron may be dense splintery and black with dull white spots anit in it again the iron and lead form a gray black hard flinty looking ore called hard carbonate yet in other places the outcrop presents an unchanged galena these varying indications depend on the purity of the ore on the nature of its enclosing formations and the degree of oxidation or weathering weathering agents commonly alter the galena to sulphate carbonate or oxide all of which are fairly stable compounds lead is not as soluble in surface waters as are copper and zinc both of which dissolve out and migrate downward leaving le ached barren outcrops so owing to its stability in the oxidized zone most of the deposits of lead are good and even rich right from the surface in many instances this has proved to be the only bonanza zone in the example of a mixed ote ore of copper coper p zinc and lead where the copper and zinc have been leached beached oue out leaving the lead as a residual concentrate bonanzas have resulted the common tendency of the surrounding sedimentary formations is to assume bleached and lighter colors the blue and black limes may change to brown but more often to light yellow or white marble and show fracturing the changes that take place in the quart tend more to shattering and softening than to discoloration the chert I 1 beds are usually altered to nodular fragments and yellow clay not all these indications will show at any one place and only a few of them in most places but on the whole there is presented a faded plainness and lack of boldness and color which make them distinctive mineral belts the term mineral belt was employed by the early miners of the west to express the same idea that copper range and iron range do in michigan and wisconsin its meaning is that veins and sy systems sterns of veins and other deposits of ore tend to inhabit and run with particular formations and kinds of rock for long distances in recent years the terms metal ogenia and provinces have come into technical use to express similar but more scientific ideas in the early days this entire mountainous region was new and unknown to all alike the pioneer prospector had no maps nor books to guide him to favorable mining localities he had to discover them one by one by goiny going b everywhere at much labor and loss of time nevertheless he discovered all our mineral belts these belts occupy about 10 of the mountainous areas by concentrating his energies along the trend of these mineral belts the modern prospector can save much time and expense eapen se the singular thing is the mineral belts do not parallel but cut east and west across the north and south trend of the mountain ranges the government geologists call i them transverse uplifts in western utah and nevada these uplifts can be traced for hundred of miles reference here will be made to only three of them the tintic gintic deep creek uplift rises near santaquin San strikes west via eureka dugway and deep creek utah ely white pine E ureka eureka and austin in nevada and beyond this belt is miles long the uinta bingham uplift rises east of park city and trends west via the cot ton woods bingham thence detours around the north end of the grantsville Grants ville range thence toward wendover utah thence westward across silver zone pass the pequop pequot and high ruby and diamond range south of the humboldt river and westward to battle mountain nevada this belt is nearly miles long the bonneville uplift forms the watershed between lahontan and bonneville basins and snake river in northwestern utah biah and northeastern nevada north of the humboldt river it rises in the raft river liver range in utah with the century and districts district 5 as indicators and strikes west via delno contact jarbidge harbidge Jar bidge mountain city old tuscarora to gold circle and beyond in nevada this belt is 20 miles wide by miles long for years all three of these extensive belts have been prospected for gold silver and copper coppe r but not for lead where and when lead has been found it was a disappointment in that the search was made for something better now most if not all the intrusive granites goranites gra in these three belts are of the intermediate lead expelling kinds namely tra chite diorite syenite and their phases which have intruded everywhere extensive lime shale and quartzite formations verily those in need of or who wish to search for lead deposits will find these fields pregnant 1 1 J with opportunities in which to explore more than to deplore |