THE IMPERIAL LODE LAVA BEDS DISTRICTSAN BERNARDINO CO. CAL.VEIN CUT BY INTRUSIVE DYKE OF FELSITE
THE IMPERIAL LODE LAVA BEDS DISTRICTSAN BERNARDINO CO. CAL.VEIN CUT BY INTRUSIVE DYKE OF FELSITE
Since the formation of the Imperial lode there has been considerable movement within the vein itself. Slips are numerous, the slickensides showing plainly. The fault planes, as far as observed, are confined within the limits of the vein; however, at no place, excepting where the dike intersects it, did I notice any lateral displacement.
Usually the vein is distinctly separated from the inclosing rock, aclay selvage marking the line of the fault plane on either side. In some instances, however, where a brecciated condition of the quartz porphyry is found in contact with the vein, the ore has been deposited to some extent in this broken mass, and in such cases the line of demarkation is not at all plain. These occurrences, together with the branching spurs, seem to indicate perfectly the character of the vein, which before the intrusion of the felsitic dike was more simple than we now find it. My conception of the Imperial vein is that a great fissure formed in this mountain range; that at the time this disruption occurred the hanging wall side of the fault slipped downward, causing a further fissuring and crushing of the rocks on that side of the fault. It is a notable fact that all the branches or spurs of this vein occur in the hanging wall country and are directly connected with the main fissure. This idea is still further substantiated by the additional fact that all, or nearly all, the crushing and grinding adjacent to the fault plane has occurred on the hanging wall side.
Occasionally, in the narrower portions of the vein, a banded structure indicates the probability that the ore now fills what was at one time an open crevice, which slowly filled with ore by precipitation from the mineral waters passing along the fault plane.
At one point on the course of the vein, where it is joined by one of the branching spurs, the felsitic dike has intersected the smaller vein. The occurrence is plainly seen in a cut made at this place, where rich ore was found.
THE FELSITE DYKECUTTING A BRANCHING VEINIMPERIAL LODE
THE FELSITE DYKECUTTING A BRANCHING VEINIMPERIAL LODE
It will be noticed that both the main vein and the spur occur in the quartz porphyry, and that the red felsite cuts the smaller vein. The displacement on the surface along the strike of the vein is nearly 40 feet. This does not show in the cross-section.
Since the formation of the Imperial vein the mountains have suffered great erosion; the highest point along the croppings rises fully 800 feet above the neighboring cañons.
Although the Imperial vein is a fissure of great length and depth, all the material that is included between the porphyritic walls is not pay ore. The ore occurs in shoots of greater or less extent, the same as in any other vein. The gangue is chiefly quartz, having a pearly luster resembling in appearance some light grayish lead carbonate at a casual glance. Accompanying the quartz, though in minor quantities, are baryta, calcite, and black manganese oxide. The value of the ore lies almost wholly in its silver contents, which occur as chloride and sulphide (argentite) accompanying pyrites, chalcopyrite, and iron oxides. The silver sometimes occurs with copper glance in small bunches in solid masses of lead carbonate. Such ores are very high grade. In one of the branches gold is found with only a small percentage of silver, the reverse condition, however, usually obtains. The silver frequently is found in the same shoots with the base ores and in quartz without any intimate association with either lead, copper, or iron. The galena is sometimes very low grade, carrying only 4 ounces per ton in silver. In one shoot the lead carbonate contains over 200 ounces. It is a notable fact that no good ore is found in quantity without copper in some form, either as sulphide (glance) or carbonate. Chloride of silver is also found associated with iron and manganese, without copper or lead.
There are six lode claims located on the Imperial vein, on all of which considerable work has been done. Beginning at the east end, the vein shows itself on the mountain side close down to the desert wash and not far distant from the basalt flow on this side of the range.
The most easterly claim is called the Sampson, and from it has been shipped some rich ore, the claim producing the highest grade ore, I am told, of any mine on the vein. This claim is joined on the westward by the Morning Star, a deep cañon separating them. From the bottom of this cañon it is 800 feet to the summit of the mine, 1,500 feet farther west. The Morning Star Mine has been quite extensively opened by tunnels and shafts, but for several years past assessment work only has been done, as the ore which was found was too low grade to make shipping profitable.
The Meteor, Mammoth Chief, and Desert Queen succeed each other, respectively, going west. On the Mammoth Chief and Meteor, a great deal of work has been done; and it is claimed ore was shipped approximating $40,000 gross value. At any rate the owners have developed their claims and made a good living at the expense of the ore thus shipped from the vein. On the Meteor a shaft has been sunk a depth of 100 feet, at the bottom of which a drift 40 feet in length has been cut along the vein on an ore shoot which was followed down from the surface. At another point on this claim a shaft of 65 feet in depth has been sunk in ore. A drift at the bottom of this shaft is also in ore, 8 feet of which is exposed and the foot wall not yet reached.
The ore at this point is said to average 30 ounces. I was told that the average of the ore throughout the mine was about 25 ounces, ranging from 12 to 75 ounces, and occasionally much more. Numerous cuts, shafts, and drifts, some of them of considerable size, have been madealong the vein on the Meteor and Mammoth Chief for a distance of 800 feet, and although these workings are not connected they have the appearance of being on one shoot of ore. One fact is very evident from an examination of the mine, and it is one of considerable importance. It is, that the ore is of better grade and occurs in greater quantity in the vicinity of the felsitic dike, which, though undoubtedly later than the vein itself, seems to have enriched the ore very materially. The largest shoot of ore I saw has formed very close to the point of intersection of the felsitic dike with the main vein. On the Desert Queen a long tunnel and several crosscuts have exposed ore bodies, some of which contained upwards of 200 ounces silver per ton.
The Imperial lode is one of the most promising veins of which I have any knowledge, but it requires considerable capital to properly and systematically open it. The rock is extremely hard, and the lack of wood and water are drawbacks which prevent the owners from working the mine as it should be worked. It would be difficult to find a vein offering greater natural advantages than are found here, excepting as to wood and water, both of which are obtainable under the usual conditions attending that problem on the desert. Water can be found in the dry lake 3½ miles distant by road, and 1,160 feet below the level of the cañons which cut the vein.
Coal may be delivered at Lavic Station, 5 miles from the lake, for about $9 or $10 a ton. The difficulties are no greater than at Calico, where they seem to have been overcome quite easily. Tunnels may be run in on the vein, getting average backs of about 350 feet above the bottom of the cañons.
Should ever this great vein be worked on a larger scale with abundant capital, a tunnel started at the lake will cut the vein at an average depth of 1,500 feet. Such a tunnel would probably be about 12,000 feet in length. The ore shoots seem to have an average width of about 5 feet as far as exposed, and none of the workings in ore have ever reached the bottom of a shoot. It is one of the most imposing looking veins I ever saw. On the Desert Queen the soft hanging wall has been eroded, leaving the vein standing exposed for fully 80 feet in height.
About 4,000 feet south from the Imperial lode there is a mine of unusual character and interest, called the Tiptop. Originally a silver mine, it is now producing a high-grade copper ore, which is being shipped to Swansea, Wales.
The Tiptop was discovered in 1890, by the strong outcrop of an ore shoot. The country rock on both sides of the vein is quartz porphyry, similar to that inclosing the Imperial lode. The ore occurs along a fault plane, or rather a series of parallel faults, as the result of substitution of ore for the original rock. The faulting of the rocks has resulted in an extensive crushing and breaking up of the porphyry along the line of fracture, exposing large surfaces of rock, thus facilitating the deposition of mineral. As mentioned above, the faulting seems to have consisted of several fractures, nearly or quite parallel, between which the rock was crushed or ground to powder. In places this ore body would seem to possess well-defined walls, but moving in either direction along the strike of this zone the “wall” proves to besimply a faulting plane, beyond which ore again occurs. The result of these parallel fractures is to give to the deposit an appearance of banded structure, like that sometimes noticed in simple fissure veins. This apparently banded structure is entirely due to the planes of displacement.
CROSS SECTIONOFTIPTOP MINE
CROSS SECTIONOFTIPTOP MINE
Doubtless this faulting extends to great depth, though the mineralization is not continuous along the surface for more than 150 feet. At some distance, however, and in line with the strike of the displacement, other ore bodies appear. The ore body where the discovery was made is heavily mineralized with iron oxides, of red, yellow, and black colors.
Much of the original rock has become silicified and bleached to snowy whiteness in the lower part of the deposit, but such masses contain only finely disseminated iron pyrites, low grade in silver. The once sulphuretted ores are so thoroughly oxidized in this surface deposit that they are very porous.
The ores carry on an average about 30 ounces of silver, and for the most part are very free-milling. At the time of my visit an estimate of this silver ore on the dump and in the mine placed its value at, approximately, $20,000. In one portion of this rather remarkable ore deposit considerable quantities of native sulphur occur, associated with a brownish iron oxide and silicious gangue material. As depth is attained the oxidation is less marked, and at 80 feet has apparently given place entirely to sulphuretted ores and silicious rock, low in silver.
The strike of this shoot of ore is north 50° west, dipping northeast at an angle of 70°. At the depth of 65 feet below the croppings, in sinking a winze, which in its downward course follows a slip northward but is vertical as compared with the dip of the vein, a bunch of high-grade, partly oxidized copper ore was discovered. Further development discovered other pockets or bunches of copper ore carrying usuallyabout 15 ounces in silver per ton. When a depth of 120 feet had been reached a crosscut tunnel was run in 235 feet. The course of this tunnel is north 5° west. The face, however, had not reached a line representing the dip of the surface shoot. The tunnel has been connected by winze with the upper workings, and considerable other development accomplished.
By means of these workings the peculiarities of the mine have been exposed. The series of faults which have resulted in the deposit of a considerable quantity of silver ore have been accompanied by another series of fractures which, while independent of the former, were, perhaps, contemporaneous. The second series exhibit no parallelism, but strike in various directions. Along these fault planes occur bunches of copper ore, principally variegated pyrites (bornite), chalcopyrite, and a black “earthy” sulphide, having a shining streak, not sectile, probably a variety of copper glance.
These ores are sometimes associated with iron sulphide, but most of this class may be easily sorted. One class of ores occurs intermingled with the gangue containing about 15 per cent copper. This ore can be separated on any concentrating machine such as a jig, the resulting product being high grade. The ore shipped to Swansea has averaged over 33 per cent copper and 15 ounces silver per ton.
LONGITUDINAL SECTION OF TIPTOP MINELAVA BEDS DISTRICT SAN BERNARDINO CO.
LONGITUDINAL SECTION OF TIPTOP MINELAVA BEDS DISTRICT SAN BERNARDINO CO.
The Tiptop consists of two claims. The easterly one, the Kenton, has little or no development, though copper carbonates have been discovered on the ground. All of the workings of the Tiptop that are in copper ore, it should be remembered, are in the country rock on the foot wall side of the series of faults in which the silver ore occurs, and no drift or crosscut had been run into that zone below 80 feet from the surface. The face of the drift on the third level had exposed about 6 feet of good ore at the time of my examination. The drift at that point was 160 feet from the surface. It is not likely, should a crosscut berun under the silver ore shoot from the lower levels of the mine, that oxidized ore will be found at that level, but it will be interesting to know what sort of ore may be found there. Indications of copper on the surface are very slight. In a few places stains and thin seams of copper carbonates occur in the fracture joints of the country rock, but there is nothing to lead one to believe that ore lies beneath that will bear shipment to Europe and return a handsome profit to the owners of the mine, yet such is the case.
Less than a mile from the Tiptop, in a northwestern direction, is another property, the Gladstone, locally known as Halberg’s Gold Mine. It was located several years ago, and after some development was practically abandoned, but afterwards came into the hands of the present owners, who have developed the ground quite extensively, built a long tramway and ore bins, and established a camp.
Nothing was being done at the time of my visit. The mine is something of a curiosity geologically and mineralogically. The ore body, for there is only one of any consequence developed, occurs in the gray quartz porphyry common to the region. A fault has also occurred here, fracturing the country rock in a manner similar to that in the Tiptop, excepting that here there is but a single, simple fault. The ore body consists of a mass of crushed and broken country rock, portions of which still show distinctly the original porphyritic structure. Generally speaking, however, the original rock has undergone an extreme metamorphosis, resulting, in most cases, in more or less complete mineralogical and physical changes. The porphyry has, by gradual replacement, been changed to solid ore, or been silicified to a dense quartzose, sometimes jaspery, rock. Kaolinization of the feldspars has also taken place. As to the origin of these deposits there seems to be little reason to doubt that the ore was deposited by percolating waters, which derived their contents from the neighboring eruptive rocks. These solutions were carried into the fault plane, and reaching the great chamber or crushed mass, found conditions of a superior nature for the precipitation of the minerals they contained. In the pulverized or finely crushed portions the ore deposition has been most complete, entirely replacing the original rock, while in the brecciated portions the ore occurs as incrustations, filling the smaller interstices, but sometimes penetrating the rock fragments themselves.
The ore body is something over 200 feet in length and 30 feet or more in width at the Widest part, but thinning out rather irregularly toward the ends and also downward.
Doubtless it at one time extended some distance upward, but that portion has been eroded. Along the plane of the fault the line of demarkation between ore and porphyry is very distinct, as the two bear not the slightest resemblance, but at the outer edges of the deposit no such line can be discovered. The mineral gradually disappears, leaving only a brecciated mass of whitish rock, which graduates into the normal porphyry. The brecciated condition of the mass is made more plain by the variety of color assumed by the angular fragments. They are various shades of green, red, white, and brown, or yellow, caused by copper carbonates and iron oxides.
Though the original condition of the ore was doubtless sulphide, it now contains, as the result of oxidation, hematite, limonite, magnetite, malachite, azurite, chrysocolla, cerussite, wulfenite, chloride of silver, manganese oxide, and metallic gold. The value of the ore lies principally in the gold contained, though in one portion of the ore body, near its eastern end, rich chloride of silver ore is found, with but little gold. The physical appearance of the ore is no criterion of its gold contents, as two pieces, with identically the same characteristics, will differ widely in value. One may contain $2 or $3 in gold, the other several hundred. Should ever a mill be erected in the district, this ore can be worked to a profit, though this single ore body will alone scarcely justify the construction of a mill.
On the south side of this fissure or slip is a vein which runs nearly parallel with the chambered vein above described. This vein can be traced for several thousand feet. In character the ore is similar to that found in the Imperial lode. Assays running over $200 in gold have been obtained from this ore, and $50 assays are not uncommon. The vein is quite small, ranging from a mere seam to 2 feet. Scarcely any development has been done on this vein, though it promises better results than the large “vein chamber.”
The developments on the Gladstone consist of a shaft 60 feet deep. The first level is cut at a depth of 30 feet from the surface, where drifts have been run for a distance of 30 feet each way from the shaft, on the course of the vein, and a crosscut, 28 feet north. East of this, a 15-foot shaft has been sunk in a good sized cut. A large open cut, 100 feet long, has exposed the upper portion of the ore deposit perfectly. Other superficial work has been done at various points along the vein. A tramway of 1,700 feet has been constructed from the mine to the bottom of an adjacent cañon.
In the vicinity of the mines described in this district are numerous other claims, some of them having considerable development, but all lying idle at the time of my visit. One claim has an 80-foot tunnel, and shows some lead and silver ore of good grade. This claim is patented.
Twenty-three miles northeast from Daggett are the Alvord Mines. The property has changed hands several times, but is now owned by a party of Pasadena capitalists, who have under consideration the reconstruction of their mill, which was burned in September, 1891.
The property consists of six full claims located on one mineral-bearing zone. The strike of the belt is a few degrees south of west. The mine is well equipped. The company also owns a millsite at Camp Cady, on the Mojave River, 9 miles distant from the mines, and valuable water rights at Paradise Springs, 11 miles northwest from the mines, and a spring about 1½ miles east of the camp, which is used for camp purposes only.
The mines lie along a broad zone or belt of crystallized carbonate of lime (calcite), which may be seen for many miles traversing the dark-colored inclosing rocks. A huge dike of porphyritic rock cuts acrossthis belt at an angle approaching 90°. The principal mineralization of the lode occurs east of this dike.
The country rock is described by F. R. Burnham, E.M., formerly the Superintendent, in his report on the property to the company, as rock more or less schistose in character, through which, at frequent intervals, are intruded eruptive dikes. At the east end of the belt is an accumulation of tufa and basalt. The belt dips south at an angle of 75°. The mineralized portion of this lode extends from the porphyry dike east through three full claims, disappearing finally beneath the eruptive rock and desert wash. The dominant point on the lode is 550 feet above the base of the hill.
The entire lode is gold-bearing, some of the iron rock being extremely rich; gold also occurs in the calcite, though it is usually of a lower grade than where accompanied by the iron. Iron sulphide containing gold has been discovered, indicating plainly the origin of the slag-like iron ores and limonite found on the surface.
To Mr. Burnham’s report I am also indebted for information concerning the value of the rock, tonnage, and bullion output to date. He has given arbitrary figures for shipments aggregating $37,000, and an estimate on $13,000 more, making a total of $50,000. This ore was milled mostly at the Camp Cady mill and at Hawley’s mill.
An arrastra was used in the early history of the mine. The average assays made on a ten days’ mill run just prior to the burning of the mill returned $12 75 per ton. Tailings, during the same period, averaged $1 25. Bullion produced, $1,430. It was found very difficult to sort the ore, though it varied constantly in value from $2 to $20 per ton. About 90 per cent of the assay value, it is claimed, was saved in the mill. In looking through a daily record of assays made in July and August, 1891, I find them to range from a trace to as high as $1,750, most of them running from $6 to $18. Mr. Burnham figures 184,000 tons of mill rock in sight, including all grades, besides large amounts presumed to be available, but not blocked out for stoping. The value of the ore is placed at $5 to $6 throughout.
The cost of milling this ore is placed at $2 50, and mining at 50 cents in large stopes. Should the company now controlling the Alvord Mines determine to rebuild their mill it will doubtless again become a bullion producer.
The Oro Grande Mining District is located immediately east of the Southern California Railroad, at the town of Oro Grande. It is commonly supposed to embrace all the mines for some miles around, though, in fact each group of mines or hills has been given a separate name, but as these so-called districts are mostly without organization, all the claims and mines will be considered under one head.
The geology of the district about Oro Grande is complex, the formations being uplifted, greatly faulted, and broken, besides the intrusion of dikes of felsitic rock, diorite, and quartz porphyry. I had not sufficient time at my disposal when at Oro Grande to study out the somewhat intricate geological problem, and will describe the region in general terms.
Commencing at the town of Oro Grande, which stands on the bank of the Mojave River, the country rises in a gentle slope toward the hill half a mile distant; gently rolling hills are reached, which in turn giveplace to more rugged masses, and finally to a rough mountainous area, the hillsides being almost precipitous. The lowlying country about the base of the hills is mostly made up of schistose micaceous rocks, a quartzose mica schist predominating. The first hills of any consequence are eruptive, mostly a light-greenish felsite and a coarse-grained porphyritic rock. Beyond are prominent hills of a dense, hard quartzite resting upon a crystalline limestone, the highest hills being made up of practically the same materials (quartzite and limestone), in part schistose with some mica schist, jasper, and many intrusive dikes of all the previously mentioned eruptives, prominent among them being diorite of dark-green color.
Within half a mile of the town, and on a lower spur or ridge that makes down from the hills, is located the Embody Mine, which, during the excitement at this locality in 1890, attracted considerable attention. The gold-bearing material is quartzose, micaceous rock of somewhat friable character. The deposit, as I may term it, has the appearance of being an impregnation without definite form.
Were it not for the fact that the shoot of gold rock makes across the strike of the schists, it would resemble some bedded deposits found at the Homestake, Black Hills, South Dakota, where micaceous schists have been silicified and hornblende schists metamorphosed to chloritic schists, the whole carrying gold across a broad zone 1,600 feet in width and 6,000 feet in length. The gold occurs in shoots or vein-like zones, without defining lines of any character. At the Embody Mine, too, little development has been done to make any positive prediction as to the future of the mine. The formation strikes northeast and southwest, and dips 70° southeast.
The country is somewhat broken up, but no considerable masses of shattered rock were observed. The croppings are quite heavily stained with iron oxides of brown and red shades, and this mineralization can be traced some distance. Two shafts, one nearly 100 feet deep, the other about 30 feet, have been sunk on the deposit, exposing rocks of uniform character, all carrying some gold. The width of the gold-bearing zone is undetermined, but it is thought to be from 6 to 20 feet.
As far as I learned, a “mill-run” had never been made on the rock from this mine. Mining operations had been stopped and the property involved in some sort of dispute. The value of the rock was given to me as $8 or $10 per ton.
The principal mine of this district, and the one which gave the camp its fame, is the Carbonate Mine. It was discovered by a man named Collins, who was working in a lime quarry near by. Collins found croppings of ore—limonite and manganese—containing silver. He developed the property somewhat, but it finally passed into other hands, and is now owned by a Los Angeles company, which has opened the mine quite extensively.
The formation which incloses the vein has a general trend northeast and southwest, the dip at the main workings being not over 20°. Here an inclined shaft has been sunk to a depth of 225 feet on the vein. At the bottom the shaft has attained a vertical depth of about 100 feet.Two veins of ore, consisting principally of silicious and earthy iron oxide and black oxide of manganese with carbonate of lime, sometimes crystallized, extend from the surface to the bottom of the incline. These veins are very irregular in size, varying from a mere seam to upwards of 2 feet in places.
The value lies in the lead carbonate and silver which accompany the gangue minerals. The two veins are curiously formed at contact with massive blue limestone and mica schist. The schist is from 1 to 4 feet in width, the ore lying both above and below it, the whole being inclosed between hanging and foot walls of crystalline limestone. At various points in the workings is a light-colored, much decomposed rock, resembling felsite, which has the appearance of having been injected between the strata in a thin sheet. It is a notable fact that where this buff-colored, granular appearing rock occurs in contact with the vein an enrichment of the ore is noticeable, and its absence is marked by the low value of the ore or no ore at all. In this incline, at a depth of 40 feet, a short drift has been run in on ore of good grade. At 180 feet from the collar of the shaft the discovery was made that caused this mine, and, in fact, the entire camp, to become at once the scene of excitement.
At this place a small wedge of crystalline, granular quartz and calcite appeared, and with it flakes of free gold. Just below the point of this discovery the wedge widened to several inches, and the rock was a mass of glittering sheets and shot-like pieces of gold. Assays of the material gave fabulous returns. The ore was broken down on canvas, and every ounce of it sacked on the spot. This was followed down some distance, but gradually thinned out below the 200-foot level, where drifts were run, one 50 feet northeast, the other 40 feet southwest. From these drifts considerable rich quartz was obtained.
In the southwest drift the formation is badly displaced and broken and the vein is lost, a fault having thrown it, but whether up or down could not be determined, as the adjacent rock was so badly fractured. Ore was found at the face and along the sides of some of the cuttings, and some free gold was found on the 200-foot level in the southwest drift. All work on this part of the mine had been suspended some time prior to my visit, the mine having been enjoined.
This question is one which finds its answer, it would seem, in the fact that the sheet of mica schist included between the heavy masses of limestone represents what at one time was possibly a bed of sandy clay or mud, which with the metamorphosis of the region has become a crystalline schist. The planes separating this schist and the limestone above and that below it were evidently planes of weakness, and when the forces which uplifted and fractured the strata exerted themselves these rocks slipped and ground upon each other, causing considerable crushing along these planes; possibly open crevices resulted in some portions. Ore was subsequently deposited in these interstitial spaces, partly by substitution of ore for limestone, no doubt, and partly by precipitation in the crushed mass of lime and schist. The injection of a sheet of felsite into the same plane of weakness can easily be conceived, as such intrusive bodies always follow the lines of least resistance. The extreme richness of the rock, together with its somewhat unusualassociation of quartz and calcite, attracted no little attention to the property at the time of its discovery.
Southwestward from the deposit just described is a vertical shaft 125 feet deep. This shaft has followed down what seems to be a fissure in the limestone, in which lead carbonate, some galena, limonite quartz, calcite, and manganese oxide occur. This ore was worth at Socorro, New Mexico, $50 per ton for the gold, silver, and lead it contained, and it was shipped there in quite large quantities.
A large stope commences on the northeast side of the shaft at a depth of 30 feet from the top and extends down to the 114-foot level. Considerable ore was standing in sight in the mine at the time of my visit, but nothing was being done. The company have had to stop work, as the owners of the lime quarry claim to have this property included in their patent.
There are scores of other claims in this interesting district, but little development has been done on them. Here and there are encouraging prospects, where carbonate of lead and oxide of iron have been found; but on the most promising of these only 10-foot holes have been sunk. The mineral zones are not well defined, and the prospectors have not the capital necessary to systematically prospect the hills.
Is 5 miles south of Oro Grande. There are a number of claims, the principal one being the Amazon. The formation is similar to that about Oro Grande. In a large dike of diorite occur the ore bodies of the Amazon Mine, which produces copper ores of a fair grade. Several holes were sunk to various depths, ranging from 15 to 30 feet, by the Mormons who settled on the Mojave River years ago. Recently a shaft has been sunk to the depth of 61 feet, and a drift run north 40 feet. The ore is principally copper-iron sulphide (chalcopyrite).
The ore in this mine occurs along slips or fault planes. This peculiar class of deposits has been described under the head of the Tiptop Mine, Lava Beds District, in this county, and as the essential features of this mine are similar to those of the Tiptop, repetition here will be unnecessary. I found a greater mineralization of the limestone in this district than about the Oro Grande, though no prospecting has been done here for lead ores.
Twelve miles northeast from Victor are the Gem quarries, that produce variegated marbles of great beauty. Shades of yellow, chocolate, black, pale blue, crimson and gray, cream-colored, rose, and white. The markings are such as to produce beautiful effects. The croppings are strong, and the surface material is apparently not at all injured by the exposure of centuries to the elements in a region where nearly all rocks decay and disintegrate rapidly. The outcrop stands boldly above the adjacent country rock from 10 to 20 feet. The entire ledge or belt is made up of bands or beds ranging from 3 to 6 feet in thickness. Thesestrata are separated by thin seams or fractures, but it is reasonable to presume that this separating line or joint will disappear as depth is attained. The rock is all susceptible of a high polish, and it withstands a tremendous crushing force. It was said by the owners that this had been determined at 28,000 pounds per square inch.
The quantity is large, the variety abundant, and the beauty approaches that of rare onyx. With these unusual conditions surrounding the deposit, its marketing should become an industry of no small importance. The difficulties of transportation are not insurmountable.
Near Oro Grande and Victor several lime quarries are in operation, constantly giving employment to quite a large number of men. Lime is burned in large kilns, which finds a ready market in Southern California. Granite is also extensively quarried near each of these places, and used for building material, curbing, and paving blocks in Southern California cities. This industry employs, all told, about one hundred men.
Three miles from Hinkley Station, on the Atlantic and Pacific Railroad, between Barstow and Mojave, is located the Kent Mine, a vein covered by two claims. A shaft 80 feet deep and some superficial development have exposed the ore, which varies from 3 to 10 feet in width. The gangue is a rather fine-grained, granular quartz, containing galena and lead carbonate. Assays in gold and silver are obtainable anywhere in the vein. The highest grade carries lead 70 per cent, gold $25, silver 24 ounces. Some of the ore assaying low in lead contains gold and silver in paying quantities.
The property is in a prospective stage only, but is promising. Water can be obtained near the mine, and fuel is but 8 miles distant. The owner bonded the property in May, 1892, and it is at this writing being developed by the prospective purchasers. The ore is of such character that by sorting a milling ore may be obtained, the high-grade lead ore making a very good smelting material.
Three years ago the Black Hawk District, 40 miles east of Victor, on the north side of the San Bernardino range, attracted considerable attention through the extensive operations of an English syndicate at those mines. Development was in progress at that time, and it was planned to build a sixty-stamp mill. The quantity of gold rock, however, proved to be smaller than had been anticipated, and a small experimental mill was built; but from a short time after the completion of this mill to date all operations have been suspended, and the probability of the resumption of work is not bright.
The gold occurred in a reddish oxide of iron in bunches and stringers scattered through a crushed zone of limestone, lying along the flank of the mountains. A party, who for a time was in charge of the property, informed the writer that he had worked the rock without sorting, had endeavored to sort it, and had tried screening it, but that notwithstanding every precaution was taken, he had concluded that it could not bemade to pay. The gold-bearing rock was quite rich, but it occurred in too small quantity to make it profitable.
Four miles northeast of the Black Hawk Mines, lying down on the desert, is a formation of limestone and quartzite, resting on a massive crystalline rock, containing quartz, feldspar, biotite-mica, and hornblende. This reef extends from the mouth of Texas Cañon out upon the plain, sloping downward at an angle of approximately 5° for a distance of 4 miles, where it terminates in a bluff 40 to 100 feet in height. Along the entire eastern edge of this deposit it drops off abruptly as though sharply eroded. At the northern end the reef is faced by a low range of hills composed of the above-mentioned hornblende rock. From this point it swings west and with irregular outline extends for 5 or 6 miles toward Rabbit Springs. The entire area, fully 25 square miles, is cut by gulches varying from 20 to 150 feet or more in depth, that have been eroded through the strata and down into the underlying crystalline rocks. These cañons seem to have resulted from natural drainage, being started by slight depressions in the rolling plateau of limestone. On the extreme northern edge at one point, hills of considerable size have been formed by the folding and tilting of the strata. The limestone has been subjected to violent compression, as the whole area is faulted and broken into millions of fragments.
I have examined not less than twenty mining claims on the reef and traveled over the greater part of its area, and am sure I never saw a single piece of limestone that would weigh 300 pounds, most of the pieces measuring under 6 or 8 inches. Considerable masses along certain zones have been granulated, and even pulverized. This fractured rock has all since been loosely cemented by the infiltration of carbonate of lime into the seams. Geologists who have examined this peculiar deposit do not agree entirely upon its mode of formation. Some believe it to be the result of chemical precipitation of carbonate of lime from calcareous springs, similar to the Formation Springs in the Yellowstone Park. There are many things about Silver Reef which would at once suggest the probability of this mode of deposit, but I am very doubtful that such a theory will stand a thorough investigation.
It was asserted that at one time a shaft sunk in the reef passed through the lime deposit and into the “wash” of the desert beneath. On investigation I found that the lime had indeed been cut through, but the underlying rock proved to be crystalline hornblende rock in place, though somewhat decomposed. At any rate it was not desert “wash.” Over considerable areas the lime is underlaid by a stratum of quartzite of variable thickness, less than a foot in some places, and again in others 10 or 12 feet. Over certain limited areas quartzite is wanting altogether. The lime is mostly crystalline, varying in color. A small portion is as white as snow, the greater part is gray or bluish, and some of it black.
For fully 8 miles along the irregular front of the reef silver ores are found. The ore deposits are usually discovered by the cherty masses of silicious rock, which, being harder than the limestone, stand out from its weathered surface in bunches and small, vein-like masses. Often inbreaking the cherty rocks, stains of copper carbonate are found, and from such rock silver, and sometimes gold, is obtained. Numerous shafts, cuts, and tunnels have been made on these claims, twenty or more in number, and in every one ore of good grade has been found, although the quantity is usually small. A shipment from a claim called No. 1 returned 129 ounces per ton in the Oro Grande mill. On assaying, 20 ounces can be found on any of the claims, and rock of a higher grade running into the thousands of dollars is not unknown on the reef.
The ore occurs usually as bunches, sheets, or stringers, which “roll” more or less, but in a general way follow the stratification of the limestone downward. These stringers are from 4 inches to 2 feet in thickness, pinching and swelling both longitudinally and on their extension downward. The average of the ores thus far found is probably about $50 per ton. The mines have all been opened by the discoverers, who are men of limited means, and no systematic exploration for larger ore bodies has ever been made. They may exist, though there is no surface indication that such is the case. At one claim, No. 9, I took a large sample for 20 feet across the mineralized zone and found it to assay 11 ounces silver with $2 in gold. This rock was taken from a shallow cut 4 feet in width and 5 feet deep, 20 feet long.
The ore deposits occur without exception in zones of limestone that have been crushed into small fragments, together with much very fine material. In a few places I found in contact or close to the ores what appeared to be a thin intrusive sheet of rock of undoubted igneous origin. The original nature of this rock could not be determined, as it was very much decomposed and bleached. It looked like the white porphyry of Leadville more than anything else I could liken it to, and to a great extent has, doubtless, been the source from which the minerals of the ore deposits were derived. In many places the quartzite which underlies the lime rock contains galena, lead carbonate, wulfenite, zinc-blende, iron sulphide, copper, gold, and silver. Some of this rock contains sufficient lead to be classed as a smelting ore.
The ores of the limestone deposits are chiefly chloride of silver and embolite (chloro-bromide of silver), which is usually accompanied by copper carbonate, sometimes a copper-silver sulphide, wulfenite, lead, and iron in various forms, in a gangue of calcite and quartz, with occasionally manganese oxide. Hornsilver in crystals has been found in the fracture joints and in small cavities of a pure blue limestone, taken from a shaft on one of the claims at the east edge of the district. Pasadena, Riverside, Daggett, and Victor people are the principal owners of claims. Timber can be obtained in the main range 5 or 6 miles back of the mines, and abundance of water can be had from the cañons in the neighboring mountains or from Old Woman’s Springs, 2½ miles east of the principal claims on the reef.
Altogether the district is a most interesting one geologically and also financially, as the high grade of some of the ore had induced the claim owners to sink considerable money in the development of their mines.
On the San Jacinto estate, which is owned by an English syndicate, are located the old Gavilan Mines, which years ago produced from quartz veins considerable gold, the rock being first crushed in numerous arrastras, the beds of which, to the number of fifty or more, are stillscattered all about the neighborhood of the mines. In later years, under American management, the quartz was hauled to a stamp mill in the Pinacate District. At the time the rancho became the property of the English people nothing had been done in these mines for many years. During the past two years the old workings have been investigated and a local company organized at Riverside to operate them under lease. At the time of my visit some workmen were industriously engaged in taking down the gallows frame of the hoist and making preparations to vacate the premises, and this in the face of the report that had gone abroad that a good-sized vein of pay rock had been uncovered at the bottom of the mine at the depth of 180 feet. I did not see the alleged ore shoot and could get no satisfaction from the men at work other than vague hints that there was dissension among the Board of Directors.
The veins of the Gavilan Mines are not large, but of good grade, occurring in a granitoid rock. Black tourmaline in a feldspathic and quartz gangue frequently accompanies the gold-bearing rock. The Mexicans worked a large shoot down to the water-line, and judging from the size and number of the dumps these old workings must have been of great extent. The Riverside people had sunk a new shaft at the extreme south end of the mine 180 feet in depth. The entire region is cut by large feldspathic and granitic veins, which course in every direction. These veins are doubtless intrusive dikes of the variety of granite called pegmatite. White scales of muscovite occur sparingly, but tourmaline is abundant.
Forty-five miles from Fenner, on the line of the A. & P. R. R., in the eastern part of the county, near the Nevada State line, is the Vanderbilt District. It lies between Palm District and Ivanpah, at an elevation of 6,000 feet above the sea. Numerous claims have been located on the veins of the district and considerable development done. Messrs. Patton, Taggert & Hall own eight promising claims, which it is their purpose to develop extensively. A shaft 4½ by 6½ feet has been sunk on the vein to a depth of 60 feet, besides which a number of shafts of lesser depth and numerous open cuts have been made, all exposing ore of good grade. The vein is of the branching kind. The veins vary from 5 to 30 feet in width, striking east and west, with a dip to the north of 60°. The gangue is quartz, honey-combed at the surface from the oxidation of the sulphurets it originally contained, small disseminated crystals of which (iron, lead, and copper) begin to show in the rock from the deepest parts of the workings. Some of the rock contains a high percentage of lead in the form of galena and carbonate, but it occurs mostly in bunches and is not evenly distributed through the rock. A shipment of 6,963 pounds to the sampling works at Kingman, Arizona, returned an average assay value of $173 50 per ton, most of which was gold. Another lot averaged $44.
Near the above described property Messrs. Simmons & Roberts have sunk three shafts to a depth of 40 feet each, and Campbell & Beatty put down a shaft 100 feet, all in ore of a character and value similar to that found in the other mines. Both wood and water are obtainable in the district, pine timber growing on the hills, and a good stream of water is flowing down into the desert only 1¼ miles distant from these mines. With the character and grade of the ores found in these veins, and the advantages of wood and water, it would seem that these minesmight be successfully operated, particularly as some of the owners are possessed of sufficient means. It is the expressed intention, however, to sink deeper and determine more fully the extent and character of the ore in depth before placing expensive machinery on the ground.
Among the mines that have attracted unusual attention in this county during the past year, the Ibex Mine stands prominently in the front rank. It is located 3½ miles from Ibex Station, on the line of the A. & P. R. R., and not over 11 miles north from The Needles. The Ibex property is in the Ibex Mining District, and consists of seven claims, which were located in 1888, now owned by residents of Riverside and San Bernardino. The principal claim is called the Ibex. The vein strikes east and west, dipping at an angle of 45°. Two shafts, one 60 feet and one 52 feet, had been sunk at the time this information was obtained. At the bottom of the 52-foot shaft a drift 38 feet in length has been run on the vein. Surface cuts and trenches are quite numerous on the several claims, and a large amount of quartz containing gold had been exposed. Free gold could be seen in considerable quantity in some of the porous quartz. The quartz is thoroughly crystalline, showing many cavities as a result of the decomposition and leaching out of the sulphuretted minerals it originally contained. These cavities are all lined with minute quartz crystals, which have been deposited evidently since the removal of the sulphides. Rock of this description is full of gold, seemingly. It is so loose in texture that careless handling shakes out the golden grains. John Anderson, of San Bernardino, one of the owners, volunteered the information that from 2 to 4 feet of this rock sampled $100 to $150 per ton. The owners had determined the latter part of April to ship this free-milling ore to The Needles, where a mill was being constructed. Some of the quartz from the lowest workings contains small crystals of pyrite and chalcopyrite, but it would still be classed as an ore susceptible of free amalgamation. The Ibex property had a promising look in the spring of 1892. Its further development will be looked to with great interest by all interested in desert mines.
Near the south boundary of San Bernardino County, and about 75 miles directly east of Mount San Bernardino, a new mining district has been organized within the past two years, and considerable development work accomplished by the claim owners, who, as usual, are men of limited means.
This district is 22 miles northeast of Cottonwood Springs, 16 miles north of Eagle Mountain, and about 6 miles south from Virginia Dale. The belt is about 1½ miles in width and 5 miles in length. The veins trend north and south.
This new district, which has been named the Monte Negras, or Black Mountain District, has attracted considerable attention by the discovery in one of the claims of nuggets of gold and quartz of extreme richness. At the time of this discovery some newspapers in this county published the report that the mythical “Pegleg Smith” Mine had actually been found, which only added to the excitement produced by the bringing into San Bernardino of several hundred dollars worth of specimens.