Show MORMON BASIN DISTRICT american sumpter oregon the mormon basin district is situated about fifty miles southeast of sumpter and on the line between baker and malheur malteur counties in oregon although the auriferous gravel deposits which cover the central depression of the basin have furnished the richest and oldest placers in the northwest and these have been profitably and continuously mined for a period of forty years the interest in the quartz mines of the district is of recent date notwithstanding the fact that the camp has shown nothing of unusual interest until within the past three years probably no other section of oregon is attracting so much attention from mining men at this time this is probably due to the fact that the geology vein formation and ore occurrence of the mormon basin district are entirely different and in striking contrast with the mines immediately adjacent to sumpter and in fact with those of any other section of oregon in the mormon basin the ore deposits occur along the contacts of various igneous dykes resembling parts of nevada and colorado while in the older districts of oregon the principal ore bodies are found in quartz veins in the argillites argil lites and granite rocks the mormon basin is traversed from easterly to westerly by a wonderful system of these igneous dykes all standing close to the vertical and seemingly paralleling each other and being fairly uniform as to thickness and no more ideal condition could exist for the formation of large and permanent ore bodies these dykes outcrop on the hills and slopes surrounding the basin but are deeply covered in the lower central section by gravels and detritus the rainbow mine owned by the commercial mining company is the oldest property and the greatest developed of any in the district it is located on the eastern slope of the basin and on the malheur malteur baker county line the property has been operated for a period of about ten years but the first seven years only in a very desultory way and it is within the past three years that the development has shown amy anything unusual the ore bodies on the upper levels were more or less crushed broken and displaced and it was not until the workings had reached the foot level that the present large bodies of free milling gold ere cre were encountered the ore zone has now been proved for a total length of over 1100 1100 feet and to carry values of well above 20 per ton of which about 80 per centis centis in free grold gold the vein is a greatly endyke of lava intruded between a dyke of basalt and a very lime the orb ore bearing dyke having been replaced by quartz and sulphides sulp hides carrying gold this dyke is from thirty to sixty feet wide and the ore ranges in from two or feet wide to over forty feet wide deD depending ending upon the extent of the crushing and replacement of the ore bearing dyke and will probably average ten feet wide the mine is equipped with hoist pumps etc and the ore is conveyed from the shaft by aerial tram a distance of one half mile and crushed in a mill consisting of seven two stamp batteries and one five stamp battery plates and wilfley tables the power is at present steam A cyanide plant for the treatment of tailings is now being installed the rainbow mine is reputed to have over worth of high grade ore in sight at the present time on the western slope of the basin is located the humboldt mine the second largest property in the district here the vein lies in a contact between a very fine grained hornblende diorite foot wall anda and a very hang ingwall the vein filling is mostly crushed and altered slate which is replaced along each of the walls walls by quartz and sulphides sulp hides forming the ore the vein will average from forty to sixty feet wide and the ore from an average of probably five to seven feet to forty feet in the widest swells the average value of the milling ore is probably about 10 a ton and considerable quantities of shipping ore is encountered at various points in the mine some of the latter is of very high grade one shipment of a few tons netting the company 1194 per ton this property has been worked d by the humboldt gold mines company but a little over one and one half years and yet in this short period over feet of development work has been done the shaft has been sunk to the foot level and an ore shoot about feet long opened on both levels the property is equipped with a modern hoist pumps and all necessary mine buildings and the ore is treated in an up to date mill containing ten stamps plates six johnson concentrators etc the ore is about two thirds free the balance concentrates and during the five months the mill has been operated it has shown a total production of about and a net saving of 92 per cent of the value of the mill headings timber is very scarce in the mormon basin district and for this reason both the humboldt and rainbow are arranging to secure electric power in the immediate future so as to conserve their timber for mining purposes among the promising prospects that bid fair to make mines in this district may be mentioned the gorman group oceola hidden treasure cleveland intermountain sunday pill hill combination and various others |