Show mines bureau invests investigates I 1 gates gold in in oil 01 1 shale and explains methods used to obtain results by thomas varley for a year or more statements have appeared in the technical press and especially in various trade journals in dichting that valuable metals such as gold silver platinum and other rare metals have been found and also have been successfully extracted from oil these reports stated that and special methods of chlorination treatment leaching and subsequent precipitation also followed by table concentration of the residues after all indicated that gold and silver and other metals could be and were successfully recovered such articles have caused much misunderstanding and as the correctness of some of the statements made in them were questioned by some of the technical journals and b y various chemists and metallurgists an invests investigation aaion of the subject was begun by the me metallurgical division of the bureau of mines in order if possible to determine to what extent if any metals 0 of f value do occur in oil and if so the feasibility of attempting 6 their recovery by the processes said to have been used for that purpose inasmuch as the bureaus station at salt lake city is investigating the recovery of oil from oil the investigation vesti gation of the recovery of metals from oil was assigned to my direction as superintendent of that station an agreement had been entered into with the owner of an extensive oil shale deposit in ill AVy wyoming oming whereby I 1 would personally collect the samples of for use in the investigation vesti gation plants visited methods of treatment before beginning the work at salt lake city a stud study was made of the process used by A M beam of denver colorado for the extraction of metals from oil I 1 then visited the mill of the american continuous retort co which is situated near the assay office of A M beam in the crushing department of the plant there was a considerable sid erable amount of oil shale which apparently had been unloaded from a car ready for treatment the plant originally had been used by the chamberlain ore concentrating co as a sampling mill and concentrator cen and the equipment therein consisted of the usual equipment found in such mills the plant has been equipped for oil shale experiments with a three hearth retort for oil extraction and another retort constructed especially for carbonizing de Z the spent shale and a rod mill was used for crushing the spent shale after the oil had been extracted the shale was according to mr lewis president of the american continuous retort co treated superintendent intermountain station U S dureau bureau of mines in hot solutions agitated 6 ted in pachuca tanks which ive were e equipped with amal amalgamation ga mation plates after a batch of ore had received this treatment for a sufficient length of time the material was treated by and the solutions from the cyanide leaching were passed through zinc boxes where any gold or silver that might have been taken into solution by the cyanide would be precipitated the residues after were pumped up to another floor and passed over a AVil wilfley fley table this table and the cyanide boxes were were the only part of the plant in operation during my iny visit I 1 observed on the table a concentrate cen which I 1 distinctly identified as lead probably a little iron and zinc and some black material which was probably pyrite which had been altered durin during the roasting and there was a very thin gray streak on the table which I 1 could not identify although it probably might have been either lead sulphate or lead carbonate the presence of lead and zinc on the table led me to believe that there must have been some of this material remaining gainin g in the elevators or pump boxes this no doubt accounted for the presence of the lead and zinc which was supposed to have come from the oil shale for it is difficult to conceive how such material would be present in crude oil shale mr lewis also showed me several pieces of blakey gold which lie he stated had been picked off the table under the microscope this material had the appearance of gold but it was associated with quartzite I 1 was handed a small piece of this material alich was picked off the table in in my presence later this was tested with nitric acid and dissolved the tests indicated that it was practically all copper however it is believed that the piece examined under the microscope contained gold but I 1 do not know and therefore cannot say it was concentrated from the shale by the wilfley table samples of oil shale from wyoming secured I 1 arrived in green arver wyoming on the morning za of may 2 9 1922 and mr himes provided every possible convenience veni ence to secure the samples of shale he had two miners and cars ready also an all engineer who had made surveys on oil his properties the party then went a short distance northwest of green river and we went up on the shale deposits and pried down with bars pieces of shale from several places these were sacked up under my supervision and expressed to salt lake city I 1 arrived in salt lake city wednesday may 3 and the shale arrived late the same afternoon experiments in the oil shale laboratory U S bureau of mines university universia sit y of utah on the green river wyoming personally supervised by lewis C karrick assistant oil shale technologist upon tile the receipt of the samples at the bureaus station at salt lake city they were turned over to lewis C karrick who conducted the distillation tests dr frederick formerly a chemist with the standard oil co who had been working on the oil shale problems connected with the recovery of oil from the shale and who had been investigating b the recovery of metals from the shale in laboratories at fort wayne indiana was detailed by mr himes to assist in this investigation and gave general directions of procedure the sample was crushed to pass a 14 inch screen all the material was then thoroughly mixed and the entire batch was quartered down to obtain a 25 pound sample for analysis this 25 pound sample was distilled in several batches in the bureau of mines assay retorts the rate of distillation was such that the oil was reduced in all cases in about two hour distillation til lation periods the spent shale was retained for further experiments the oils were tested and gave ZD ave the following results rests yield 25 gallons per ton specific gravity melting point amount of distillate from crude 3 32 0 o index value for the oil index value for the shale 1 the index value of an oil is a quantity calculated from the analytical data of the oil and is the product of the percentage of distillate to obtained from the crude oil and the saturation of this distillate to amount distillate per cent distillate per cent per cent topped to to saturation 50 cc cc 1 2 index of the index value of the shale is the product of the oil yield in gallons per ton of shale and the index value of the crude oil value of shale after the had been retorted dr who had been present during the retorting process gave instructions as to the procedure to be followed in the treatment of the residues the spent shale was pulverized so that all would pass a 40 mesh screen the pulverized material was then under the direction of dr by the bureaus analyst and assayer this was done by heating in a large gas fired muffle in the fire assay laboratory particular attention was given to see that the temperature within the furnace did not exceed C at any time during Z the carbonization in order to insure this temperature not being exceeded pyrometers measuring the temperatures were used continuously during the treatment after the entire batch was the material was divided into three parts part one consisting of 2500 grams was turned over to one of the bureaus ore dressing engineers tn for concentration tests which are given elsewhere in this report part two was also turned over to the same engineer for tests and another equal part was retained for the chlorination test chlorination test tile the portion set aside for this experiment was treated under the direction of dr in a small rotary retort in the oils oil shale liale laboratory this was especially desirable equipment for the reason that proper heating and agitation could be procured allowing the chlorine gas to react on the material properly the retort was maintained at a temperature pera ture of approximately throughout the chlorina tion treatment in each test about one hour was required to complete the absorption of the chlorine gas by the shale the chlorine was drawn from a cylinder and then passed through a sulphuric acid solution and led into the retort through a special gas tight fitting the gas as was liberated at tile the back end of the shale container and any excess chlorine and also any voluble gases or vapors liberated escaped from the retort through the delivery tube which led into a gas 1 washing t bottle containing pure water four 1 pound samples were treated identically and were ultimately bulked together into one composite sample the delivery tube from the retort as well as the connections to the wash bottle were all cleaned with a dilute hydrochloride acid solution the washings were added to the composite shale sample and enough water added to procure an even mixture this mixture was agitated for an hour on the rolls and was then filtered through a suction filter during the filtering about 12 washes were given the residue the last few washes beinor being with hot water the filter cake was then broken up in fresh water slightly acids and after thorough mixing was re filtered and washed the filtrate was evaporated down to about c c enough acid added to give a faint acid reaction and C P zinc was added gold free the residual zinc was filtered off washed with dilute hydrochloric acid several times the residue melted with test lead then until zinc free and finally cupel led in V h the usual way in order to obtain a check on the work and to get comparative para tive values on other a sample of spent shale from soldier summit utah was treated in a similar manner to the wyoming 6 shale by parallel tests each shale receiving fidei identical treatment recovering by chlorination wyoming shale utah shale sample taken pounds 40 os sample taken assay tons gold content oz gold per ton debarb shale gold content of sample milligrams vi gold recovered by chlorination milligrams per cent of total gold recovered 32 IA 74 on calculating b the amount of b gold old actually recovered asa result of the chlorination and leaching tests it indicates that only 32 per cent of the total gold in the crude shale was recovered by this method it would therefore seem that such a treatment would not be profitable as a method of recovering the gold even though commercial quantities actually existed in the shale assaying oil for gold and silver this phase of the investigation z was placed under the the immediate direction of charles G maier consulting clie chemist nilst for tile the bureau and a member of the tc technical clinical sta staff ff of the atie metallurgical research department of the university of utah it is usually claimed by those who report gold ill ia oil shale and its residues after distillation that the gold is is not determinable by a conventional fire assay but that sp cial treatment is necessary to recover the gold either for dr assay or practically in discussing this matter neatter with it seemed that his idea was that the gold 11 exist as a colloidal suspension in the oil of tile the shale a and the presence of sulphur and or organic anic sulphur compound compo uil might enable the gold to distil dastil A off ff durin during t heating and t in 1 s cause low assay values to be obtained since it was desirable in order to calca calculate late tile the re g covery of 6 gold old by any extraction method to know the actual total gold content of the original material expert eap exp firpi ments i I 1 ants were carried out to sho show nar whether the U asua usua sual assay method actually did give low results and to men indicate by where in the processes carried out as above described mr karrick it would be possible to lose gold the 11 tests were performed as follows 1 fire assays essays by the usual methods of raw spent and wyoming AVy oming shale samples and spent and utah shale no raw utah shale sample was available 2 A special assay by a method described below which eliminated possibility of volatilizing gold on the raw wyoming shale 3 the determination of the gold recovered in the leach liquors as above described obtained by mr karrick methods for 17 1 four samples of 14 assay ton each were fused with the re regular ular flux used for oxidized ores the four buttons from e each ach sample combined and cupel led in the usual manner methods for 2 the organic 6 matter in a raw shale sample was completely destroyed by chromic acid all gases given off by the oxidation being washed to prevent loss no external heat was used the procedure was as follows one assay ton of raw shale was placed in a liter flask provided with a funnel inlet and an outlet tube passing a catch bottle and a wash bottle the flask contained 25 c c of water at the start c c of concentrated cent rated sulphuric acid was added through the funnel the apparatus being kept closed during the run then c c of saturated chromic acid solution were added in small portions as limited by the course of the reaction in the flask after the action had for the most part ceased 25 c c more of chromic acid were added and the whole allowed to digest over night in the morning the contents now completely deprived of organic matter were diluted with water and the colorless residue filtered out for assay the filtrate was treated with excess ferrous sulphate to precipitate any dissolved gold filtered re and the ignited papers added to the previous residue grams of raw ore gave a residue of grams the residue was washed free of chromium by re pulping with dilute hydrochloric acid and finally dilute sulphuric acid method for 3 the leach liquor from chlorination was treated with gold free zinc dust the residual zinc filtered off washed with dilute hydrochloric acid several times and the residue melted with test lead and until zinc free then cupel led in the usual way the results obtained in these tests are shown in tabular form below wyoming g shale utah shale calculated to calculated to raw shale gold raw shale I 1 i raw shale contents oz per As so 30 I 1 As 30 90 ton determined shrinkage determined shrinkage straight assay 02 special assay 02 spent shale shale av in view of these results it is concluded A that the samples tested contain minute amounts of gold to the extent of possibly 40 or 50 cents per ton pi of original shale but the amount found is not of commercial value B that no special precautions are necessary in assaying shale for gold and that any direct assay by a reliable method will give the true gold content of the original material C that there is no loss by volatilization in these samples either during the distillation of the oil or during further heating and which is greater in amount than the limiting accuracy of a gold assay at its best D that the chlorination treatment of see mk Kar barricks ricks statement for method of shale was totally unsatisfactory as to recovering what little gold is present E that the original tested do not show sufficient gold to make it worth while to attempt to recover it wyoming shale table concentration test twenty five hundred 2500 grams of oil shale from green river wyoming were concentrated on oil a small laboratory size wilfley table the 1st alst 2nd and and 3rd ard cuts or concentrates from the first tabling were re cleaned by re tabling the products from the second tabling were dried weighed and assayed the result of the test i is s as follows assay oz per per cent in gm ton au covery au |