PeterM
Well-known member
Non-Assayable Ores By Peter Mikelis
What is a non-assayable ore? One that contains precious metal values, that will not in the raw state show these values in a fire assay or other methods of chemical analysis as normally used.
There are now test methods available that can show the presence of these elements in the order these methods include the plasma arc spectrograph, neutron activation, electron microprobe, and x-ray diffraction. However there are cases, that gold did not show itself without a prior de-complexing pre-treatment to condition the ore.
The old assumption is that if it didn’t fire assay it couldn’t be there, has been discarded by all but the most stubborn or least knowledgeable assayers.
When I first began the study of the puzzle of the non-assayable I could count on one hand the people known to be interested in the problem has more has come to be known about the ores, many more people became involved in the study of the problem. The fantastic possibilities of being to recover the precious metals from these ores are readily apparent.
In the following notes, I will try to briefly outline the nature of the problem elements as I see them. The way in which the metals are tied up in ores, and the kinds mined.
Knowledge of the existence of the non assay type ores is not a new phenomenon. I helped to build a plant to try and treat one of these ores 46 years ago. I’ve often wondered if the old accounts of alchemy were not rooted in this same form of wild reactions, but probably not.
Many of the reported results were similar to the unexplained reactions found in the research efforts of today. In fire assaying it is assumed that in the testing for gold and silver in properly prepared sample repetitive results should not vary more than 5 or 10 percent. This is true where the metals in ore are in a normal metallic crystalline state.
It must be remembered that in order to have a crystal of gold large enough to see, many atoms of gold must be present these atoms must crystallize into the gold structure with a minimum amount of impurities. In the past these assay problems have been often blamed on the gold being in a colloidal form or as chlorides because chlorides are known to volatilize. Many years ago tests were made that proved these beliefs unfounded.
Since the gold is not in a crystal or a colloidal state, they must be in compounds with other elements in the rock.
Such compounds must necessarily be in a very complex nature. However, in these complexes, it is assumed that wet methods of taking the elements into solution would break down the complexing elements.
The precious metals should then be recoverable from the solutions by normal chemical procedures.
In some cases in some ores, this was found to be true.
Most of the ores that could be treated in this way were found to have values that could be identified by normal test procedure. Most methods in use at this time for this purpose involved the use of aqua regia, cyanide in some form, or thiourea.
The ores in which the non-assayable values predominated would not respond to these methods. Therefore the problem of the nature of the elements must be more basic than the size of the particle or simple recognized compound. By the time research had let us in this direction, I began considering the possible basis of the problems to be in the electrical nature of the individual element itself.
If elements refuse to act as normal stable elements, it is logical to assume they are not normal stable elements. If an element is identified as the measure of energy force in motion, and that mass does not properly identify itself, then there must be some abnormality in the structure of the mash or the motion of that mass.
Space does not permit a discussion of this fascinating possibility. However there is considerable research data able to strongly suggest that the nature of the structure of the atom is the root cause of our problems. I would be happy to discuss these possibilities with interested parties.
From the above assumption our work took a new direction. First, some form of alteration in the nature of the elements seemed necessary in order to produce a stable product.
What will alter the electrical nature of the element? Obviously some form of electrical energy or current. Electrical current can be applied to wet solutions or a molten mass in an arc furnace. Other energy forms influence the ores such as X-Ray and energy bombardment.
Roasting of ores for the purpose of oxidation, is a sometimes done with tellurides and sulfide ores. Here, external heat as energy and the flux combination as the reactive mass enter into the reactions that occur.
So, to familiarize these conclusions: First, we have an ore containing many elements. These elements are very complex compounds. The elements themselves have an abnormal electrical configuration. Therefore, to produce a marketable product, we must break down ores to reduce the complex compounds, alter the structuring of the elements, and separate the desired elements from the other elements in the ore.
Methods such as wet treats by aqua regia, urea, or cyanide will work only on normal element or after the non-assayable all elements have been normalized by some form of pretreatment.
Smelting of ores is limited by the same problem, ores must be pretreated or fluxes must be used in the smelt to normalize the element in the fusion.
Once you know where is treated for stabilization of the elements or extracted by the wet method,
values may be recovered by resins, electrolysis, or precipitation. Resin or zinc precips are highly concentrated and easily refined. Other forms of precepts such as hydroxides or sulfides are usually bulky in volume and require smelting with a collector before refining.
Treated may be smelted with the lead, copper, silver, as a collector. What is cheaper to use and is easily refined? Smelting is an expensive procedure that can only be used if high values are covered. Wet treatments are much cheaper to use that usually recover much lesser value from the same material. The profit line will determine the best method to use.
Before discussing process methods, let's take a look at the kinds of ore that may have a non assayable precious metals present. Strangely enough, for all practical purposes, for every ton of assayable quartz-type ore, there are many thousands of tons of the primary ore that is non assayable.
Quartz ores are secondary deposits of precious metals formed when the non assayable form of the elements go into the groundwater solution and re-precipitate with the silicon. In most places, when we have learned the nature of the non-assayable ores, there are readily seen as the source rock at the sight of a quartz gold mine.
It has often been said by the old time prospectors that iron is the mother of gold. There is more than a little truth in this saying. Most of ores of the non assayable type have high iron content. Probably the most prevalent element in the complex compounds is the iron with silicon as the second the silicon does not necessarily occur as a quartz.
The granitic rocks are the most likely to carry non assayable precious metals, especially the granites that readily oxidized and decompose and have a high percentage of blacks sand concentrate.
The ultra basic products of the green stone type often carry the non assayable metals. True iron ores that I have tested from Alaska and many places from the Western United States carry non-assayable metals and often have high values in the Platinum Group elements.
Some basaltic rocks carry precious metals but in my experience, to a far lesser degree then the mantle granites or a deeper seated iron ores.
Ores containing iron sulphides in many forms carry concentrations of the non-assayable metals. Many mines have been productive in the near surface zones. The difference being, the action of the nature of oxidation of the iron compounds, made the precious metals available to extraction procedures when in use.
The deeper sulphides usually carry higher concentrations of the non assayable metals. These raw sulphides may or may not fire assay, as normalization of the elements does necessarily occur during the secondary deposition.
Most sulphides will not fire assay without pretreatment to normalize the elements and breakdown the element compounds.
In the form, most sulphides have been treated by a simple air roast. This will oxidize the iron to some extent but does not necessarily alter the electrical configuration of the non-assayable metals to the assayable form. Control of temperature and the addition of proper fluxes are necessary to make the roast produce an identifiable product.
In addition to the above mentioned ores we have large deposits of sedimentary ores. The nature of the settlements may or may not be the same as the original rock, depending on the degree of alteration during the period of erosion and deposition of the rock complex.
Some sediments have assayable precious metals but most do not. Assayable values are usually the result of oxidation of the metal complex in the original rock. Simple oxidation does usually alter the configuration of the element to an identifiable form.
The most common sediments are the sandstone, shales and schists. Conglomerates do not usually have significant amount of non assayable elements.
Some of the better-known sandstones are in the Llano uplift area in Texas, and the Colorado basin that occurs in several States. Shales and schists occur in many areas. Those I have investigated and tested include the Dragdon slates in Northern California, the Riggins schists at Riggins,; a massive schist bed South of Salt Lake City in Utah; and the Cle Elum schists in central Washington.
A great deal of work was done in trying to process the ores in the Taneum mining district which covers a good deal of the Cle Elum shists area. This is a large area of several square miles. A great deal of research work I have done has been on this ore.
It has been known for over 46 years to me that the Taneum schist contains values in precious metals that would not assay. During tests work on the Taneum schist, the Riggins schist, and a number of other ores of a similar nature; it was found that several basic similarities in the chemistry and metallurgy of the precious metals were common all of the ores. Since, if the key to control of these reactions could be identified in one ore, it could likely be adapted to other ores as well. I have concentrated most of my efforts on testing methods of treating the Taneum schist ore. What are these, common factors? First, few of the ores of whatever type, will fire assay in the raw state. When fire assays did give positive results, the values can be high at times but repeat assays will seldom give the same result twice.
Second, when you start treating a new ore, if you try 25 differ treatment methods, 15 of them will give you a high test result. When you go to duplicate the treatment that gave a good result, you will be lucky if one of them will give even a close repeat of the first result. The best way to go bananas and this business is to try to get any method to do the same thing twice.
Ores of a similar type such as an iron ore, schist ores, sulphides, or black sands, who have certain common chemical reactions. Since no two ores have the same values in the same element complexes, how do you determine that the ore in question has values? If it won't fire assay how do you test it?
If you can afford it, the logical step would be to send it out for the sophisticated tests previously mentioned. Several universities now have the equipment to make these tests. What these tests will tell you is whether or not these elements are present. They will not tell you how to get them out of the rock and its salable form. A researcher who has the money or the equipment for this kind of testing obviously has a far greater knowledge than I, so any help I may be able to give another, we'll have to be of a similar nature.
Again, a brief summary of the nature of the problem is in order. First, the metals in the ore do not fire assay. To have a product we must extract the elements in a form in which they will assay.
We have two choices. Pre-treat the ore so it will assay before extraction, or extract the non assayable elements from the ore and treat them so they form a normal element.
Either method of approach to the problem must reduce the complexity of the compound, alter the electrical level, and change the oxidation state of the elements.
Pre-treat usually revolve around a change in the oxidation state by roasting, or electro-oxidizing the ore in wet slurry by electrical current.
Roasting to be successful must have flux combinations that offer an oxidizing effect, decomposition of the complex compound, and reforming of the element into new and simpler compounds of a stable nature. Needless to say, exploring these possibilities will require some work.
Electro-Oxidation methods offer a simpler approach with fewer variables to consider. Most of the work I had done has been along this line.
Introducing electrical energy into a molten mass or wet slurry of the ore has given the most consistent positive results. Whichever way the pre-treat is done, the treated ore must be processed for the extraction and refining of the precious metals.
The alteration of the electrical structure of the element has been found to occur during a physical or chemical change of the reacting media. In the molten state using the smelting method, the change occurs during the melting or the cooling and crystallization of the melt media. In electrical arc smelting, the passage of a current through the molten mass aids in the altercation of the elements.
Toward this end was a method developed consisting of an electrical arc smelt using lead as a collector, and electrolytic separation of the precious metals from the lead. The procedure is called a recycle method as the cathode lead and the slags are remelted in a closed circuit.
The anode muds from the electrolytic separations are refined for the precious metals.
The wet method of treatment involves electro-oxidation of the ore as a pretreatment, and recovery of the values by leaching of the ore in a suitable solution. The filtered solutions may be electrolyzed, run through resin columns, or precipitated depending on the type of ore and the leach solution used.
These are generalizations, but each has its own characteristics, and the method must be matched to the ore as all ores will not respond to any one method.
From the various types of ore, let us first consider the black sands. These sands are nature's concentrates of non-oxidized iron compounds that usually come from a granitic source. They are found all over the country wherever granite mantle rock intrusive occur.
These black sands do not usually contain free gold. Where it does it is easily removed and will not here be further considered. Gold locked up in the sand iron is the target. There are usually magnetic and non-magnetic sands together. The first step is to magnetically separate the two fractions. The values may be in either or in both fractions.
Since the contained elements are in compounds on the molecular level, simple grinding fine is unlikely to produce the gold in a crystalline state that may be recovered by normal extraction method. The finest possible from a practical cost basis is necessary. The smaller the rock particles the more available the element becomes to be affected by further pre-treatments and final recovery.
Where black sands have free gold present, they will often yield values by find grinding with suitable chemical. The simplest is using an oxidizer and a detergent, followed by amalgamation. It is not unusual to recover from 10 to 30 oz of gold per ton from sands using this method.
The above will recover mostly gold. To recover a greater amount of silver and the Platinum Group metals, the following should be used. First, fine grind the sand in a hypochlorite solution. Decant and filter the solids. Dry and roast the ground sand in a suitable oxidizer at about 1500 degrees Fahrenheit. Amalgamation or wet leaches can be used for partial recovery at this point. Smelt the roasted sand in an arc furnace using lead or copper as a collector to a temperature of 2800 to 3000 degrees Fahrenheit.
The iron will be reduced to iron metal and will give up a great deal of the contained values to the collector. The iron should be poured into an anode bar by melting in an induction furnace. The iron bars should be broken down in a dilute solution of hydrochloric acid. If lead is used as a collector the bars may be reduced in Floroborate or dilute nitric acid solution. Values will be recovered from the resultant anode muds. The anode mud is to be treated by the recycle method as mentioned above for the best yield of product. Another source of the non-assayable ores is the shales or schists. A number of these deposits are now being exploited. The way in which these are being treated is not likely to recover the full potential of the non-assayable fraction. Some of the shales in Alaska, the Riggins schists in Idaho, the Mancos shale in Utah, and the Cle Elum schists in Washington I have run tests on many of these materials. Most of them gave significant amounts of the Platinum Group metals. Most of my research has been done on the Washington ores.
Since even a brief outline of the past thirty years of work in testing procedures for the Taneum ore would be too lengthy for the journal. While true iron ores are less abundant than other ores containing portions of iron or iron sulfides, they are interesting for the high-value some of them contain in all of the precious metals. I speak specifically of the heavy non-oxidized iron deposit. I have no experience with iron ores in the east.
If you have an ore that you believe has non-assessable what can you do to find if it is true? I would suggest that you test them as follows. This is the general approach I make to testing a new material.
First, find grind ore - 400 mesh. This is necessary to reduce the material to the finest possible particles to make the element available for further treatment. The grind maybe wet or dry, ball or impact, as long as the ore is reduced to the smallest practical size.
Second, make a series of acid digestions of the ore to reduce the element compounds that have the precious metals entrapped. Take a 30 or 60 gram sample and digested in hot acid solution using HCL, HNO3, and H2S04 or combination of the above. Use a 10 to 20% solution. Boil and continue to add acid until the reaction stops. Decant the solution and filter.
Precipitate the solution as a hydroxide. Filter and dry the precepts. Keep the solution. Fire assay the ore residue and dried precips. Assuming that you have assayed the raw ore, a comparison of the assay of the treated and raw ore should prove interesting.
If any positive results are obtained, go back to the saved solution from the hydroxide precipitate. This should be basic at pH 8 to 12, add HCL until the solution is pH 3 to 4.
The solution should be clear now. Add NaBH4 made up in a basic solution to the ph 3-4 solution. If a black precipitate is formed, this should be filtered, dried and fire assayed. Most of the Platinum metals and some gold will be found in this fraction if they are in the ore in a normal state.
Most of the gold and silver values will be found in the hydroxide precips. The highest gold values usually will be found in the HCL, especially if a sulphides ore is tested. The highest values in silver are usually found in the Nitric leach.
If these tests are repeated five times in the assays show different levels of results, you can be sure that the non assayable metals are present. If the total values average within 10 or 20%, you probably have a normal element or and it must be evaluated as such. If any wild reactions were wild differences in values are found, you can go to the next step. Follow the above procedures but place the sample in a beaker where it can be heated and agitated. An electrical current is passed through the solution. Carbon rods are used for anode and cathode. Current may be AC or DC at 6 to 12 volts. Try both. Keep the solution below the point of boiling to prevent excessive solution loss. Time is a factor in these tests and should start from 6 to 12 hours of digest and treatment time. The purpose of this treatment is not simply dissolution of the ore, but to add the effect of the electrical energy and the change in the oxidation state, to effect stabilization of the elements. This is a form of Electro-oxidation and is not an uncommon practice.
Depending on the ore in test, many different kinds of chemicals change my work on your ore. Hypochlorite and basic solutions may also be used.
Electro oxidation can be effective on many kinds of sulfide and pyritic type ores. A solution of HCL is added, because chlorides will reduce the sulphides. The iron is taken into solution and the sulfur will remain as elemental sulfur. Most of the non assayable values will go into the iron and maybe precipitated with the base metals. How the material is to be treated from this point will depend on the nature and the state of the contained elements.
As previously mentioned much of my research effort has been devoted to the Cle Elum schists or the Taneum or as it is common called. This material has a high degree concentration of the non-assayable precious metals. In The raw state it has a very little. At least fifty ways of treating the material have been tried. Almost every method will give positive results part of the time. None has been found to give High results every time.
A strict control of test conditions is necessary. The equipment required to maintain strict control of test conditions is very expensive. I have been unable to obtain funding to get the necessary equipment.
I presently have in operation pilot plant equipment for treating the ore with an electric smelt on the recycle procedure. By this method running 100 lb of or per day, I'm able to recover 7 oz of gold per ton of ore and 100 oz of silver.
However the positive result is that is in the proof of the values can be recovered. It remains for someone else to figure out a way to do the job cheaper.
Other wet methods as described above have at times given exceptionally high values from the Taneum. The electro oxidation of the ore has many times given values and silver over three hundred(300) ounces per ton, and a number of times over one thousand(1000) ounces. When the reaction triggers the silver, very little gold is recovered. When the action triggers the gold, a small amount of silver is recovered. The gold reaction has been found to be triggered by a low temperature sulfuric acid roast. Recent tests indicate that values in excess of 100 oz of gold per ton is feasible with the proper control conditions.
In the smelting recycle procedure, the platinum group metals show up in the third cycle of the refining procedure. Very little indication of them is found in the direct pre- treatment of the material.
A number of years ago, during a pilot plant test a procedure on the Taneum, a 10-lb dore bar was sent to the Handy and Harmon refinery. When refined, we were paid for the 2 percent platinum and 4 percent palladium in the bar, obviously showing a considerable platinum content in that Taneum material.
The platinum group metals are involved in the problems of the non-assayable. They are a part of but not the cause of the basic problem.
So, the non assayable ores for all practical purposes, are limitless in quantity. Many people are now working on extraction methods, any number of them are reported to be successful. Public knowledge of the limitless amounts of precious metals that is available with no doubt an effect on the marketplace. However, supply and demand factors will still function and the large-scale correction of gold and platinum from the non-assayable ores will no doubt require considerable time to achieve. For my part, time and money have contributed to induce me to retire from the pursuit of the non assayable enigma. To any person or company involved in the non assayable research, I will provide the information that has accumulated from the past years of work.
What is a non-assayable ore? One that contains precious metal values, that will not in the raw state show these values in a fire assay or other methods of chemical analysis as normally used.
There are now test methods available that can show the presence of these elements in the order these methods include the plasma arc spectrograph, neutron activation, electron microprobe, and x-ray diffraction. However there are cases, that gold did not show itself without a prior de-complexing pre-treatment to condition the ore.
The old assumption is that if it didn’t fire assay it couldn’t be there, has been discarded by all but the most stubborn or least knowledgeable assayers.
When I first began the study of the puzzle of the non-assayable I could count on one hand the people known to be interested in the problem has more has come to be known about the ores, many more people became involved in the study of the problem. The fantastic possibilities of being to recover the precious metals from these ores are readily apparent.
In the following notes, I will try to briefly outline the nature of the problem elements as I see them. The way in which the metals are tied up in ores, and the kinds mined.
Knowledge of the existence of the non assay type ores is not a new phenomenon. I helped to build a plant to try and treat one of these ores 46 years ago. I’ve often wondered if the old accounts of alchemy were not rooted in this same form of wild reactions, but probably not.
Many of the reported results were similar to the unexplained reactions found in the research efforts of today. In fire assaying it is assumed that in the testing for gold and silver in properly prepared sample repetitive results should not vary more than 5 or 10 percent. This is true where the metals in ore are in a normal metallic crystalline state.
It must be remembered that in order to have a crystal of gold large enough to see, many atoms of gold must be present these atoms must crystallize into the gold structure with a minimum amount of impurities. In the past these assay problems have been often blamed on the gold being in a colloidal form or as chlorides because chlorides are known to volatilize. Many years ago tests were made that proved these beliefs unfounded.
Since the gold is not in a crystal or a colloidal state, they must be in compounds with other elements in the rock.
Such compounds must necessarily be in a very complex nature. However, in these complexes, it is assumed that wet methods of taking the elements into solution would break down the complexing elements.
The precious metals should then be recoverable from the solutions by normal chemical procedures.
In some cases in some ores, this was found to be true.
Most of the ores that could be treated in this way were found to have values that could be identified by normal test procedure. Most methods in use at this time for this purpose involved the use of aqua regia, cyanide in some form, or thiourea.
The ores in which the non-assayable values predominated would not respond to these methods. Therefore the problem of the nature of the elements must be more basic than the size of the particle or simple recognized compound. By the time research had let us in this direction, I began considering the possible basis of the problems to be in the electrical nature of the individual element itself.
If elements refuse to act as normal stable elements, it is logical to assume they are not normal stable elements. If an element is identified as the measure of energy force in motion, and that mass does not properly identify itself, then there must be some abnormality in the structure of the mash or the motion of that mass.
Space does not permit a discussion of this fascinating possibility. However there is considerable research data able to strongly suggest that the nature of the structure of the atom is the root cause of our problems. I would be happy to discuss these possibilities with interested parties.
From the above assumption our work took a new direction. First, some form of alteration in the nature of the elements seemed necessary in order to produce a stable product.
What will alter the electrical nature of the element? Obviously some form of electrical energy or current. Electrical current can be applied to wet solutions or a molten mass in an arc furnace. Other energy forms influence the ores such as X-Ray and energy bombardment.
Roasting of ores for the purpose of oxidation, is a sometimes done with tellurides and sulfide ores. Here, external heat as energy and the flux combination as the reactive mass enter into the reactions that occur.
So, to familiarize these conclusions: First, we have an ore containing many elements. These elements are very complex compounds. The elements themselves have an abnormal electrical configuration. Therefore, to produce a marketable product, we must break down ores to reduce the complex compounds, alter the structuring of the elements, and separate the desired elements from the other elements in the ore.
Methods such as wet treats by aqua regia, urea, or cyanide will work only on normal element or after the non-assayable all elements have been normalized by some form of pretreatment.
Smelting of ores is limited by the same problem, ores must be pretreated or fluxes must be used in the smelt to normalize the element in the fusion.
Once you know where is treated for stabilization of the elements or extracted by the wet method,
values may be recovered by resins, electrolysis, or precipitation. Resin or zinc precips are highly concentrated and easily refined. Other forms of precepts such as hydroxides or sulfides are usually bulky in volume and require smelting with a collector before refining.
Treated may be smelted with the lead, copper, silver, as a collector. What is cheaper to use and is easily refined? Smelting is an expensive procedure that can only be used if high values are covered. Wet treatments are much cheaper to use that usually recover much lesser value from the same material. The profit line will determine the best method to use.
Before discussing process methods, let's take a look at the kinds of ore that may have a non assayable precious metals present. Strangely enough, for all practical purposes, for every ton of assayable quartz-type ore, there are many thousands of tons of the primary ore that is non assayable.
Quartz ores are secondary deposits of precious metals formed when the non assayable form of the elements go into the groundwater solution and re-precipitate with the silicon. In most places, when we have learned the nature of the non-assayable ores, there are readily seen as the source rock at the sight of a quartz gold mine.
It has often been said by the old time prospectors that iron is the mother of gold. There is more than a little truth in this saying. Most of ores of the non assayable type have high iron content. Probably the most prevalent element in the complex compounds is the iron with silicon as the second the silicon does not necessarily occur as a quartz.
The granitic rocks are the most likely to carry non assayable precious metals, especially the granites that readily oxidized and decompose and have a high percentage of blacks sand concentrate.
The ultra basic products of the green stone type often carry the non assayable metals. True iron ores that I have tested from Alaska and many places from the Western United States carry non-assayable metals and often have high values in the Platinum Group elements.
Some basaltic rocks carry precious metals but in my experience, to a far lesser degree then the mantle granites or a deeper seated iron ores.
Ores containing iron sulphides in many forms carry concentrations of the non-assayable metals. Many mines have been productive in the near surface zones. The difference being, the action of the nature of oxidation of the iron compounds, made the precious metals available to extraction procedures when in use.
The deeper sulphides usually carry higher concentrations of the non assayable metals. These raw sulphides may or may not fire assay, as normalization of the elements does necessarily occur during the secondary deposition.
Most sulphides will not fire assay without pretreatment to normalize the elements and breakdown the element compounds.
In the form, most sulphides have been treated by a simple air roast. This will oxidize the iron to some extent but does not necessarily alter the electrical configuration of the non-assayable metals to the assayable form. Control of temperature and the addition of proper fluxes are necessary to make the roast produce an identifiable product.
In addition to the above mentioned ores we have large deposits of sedimentary ores. The nature of the settlements may or may not be the same as the original rock, depending on the degree of alteration during the period of erosion and deposition of the rock complex.
Some sediments have assayable precious metals but most do not. Assayable values are usually the result of oxidation of the metal complex in the original rock. Simple oxidation does usually alter the configuration of the element to an identifiable form.
The most common sediments are the sandstone, shales and schists. Conglomerates do not usually have significant amount of non assayable elements.
Some of the better-known sandstones are in the Llano uplift area in Texas, and the Colorado basin that occurs in several States. Shales and schists occur in many areas. Those I have investigated and tested include the Dragdon slates in Northern California, the Riggins schists at Riggins,; a massive schist bed South of Salt Lake City in Utah; and the Cle Elum schists in central Washington.
A great deal of work was done in trying to process the ores in the Taneum mining district which covers a good deal of the Cle Elum shists area. This is a large area of several square miles. A great deal of research work I have done has been on this ore.
It has been known for over 46 years to me that the Taneum schist contains values in precious metals that would not assay. During tests work on the Taneum schist, the Riggins schist, and a number of other ores of a similar nature; it was found that several basic similarities in the chemistry and metallurgy of the precious metals were common all of the ores. Since, if the key to control of these reactions could be identified in one ore, it could likely be adapted to other ores as well. I have concentrated most of my efforts on testing methods of treating the Taneum schist ore. What are these, common factors? First, few of the ores of whatever type, will fire assay in the raw state. When fire assays did give positive results, the values can be high at times but repeat assays will seldom give the same result twice.
Second, when you start treating a new ore, if you try 25 differ treatment methods, 15 of them will give you a high test result. When you go to duplicate the treatment that gave a good result, you will be lucky if one of them will give even a close repeat of the first result. The best way to go bananas and this business is to try to get any method to do the same thing twice.
Ores of a similar type such as an iron ore, schist ores, sulphides, or black sands, who have certain common chemical reactions. Since no two ores have the same values in the same element complexes, how do you determine that the ore in question has values? If it won't fire assay how do you test it?
If you can afford it, the logical step would be to send it out for the sophisticated tests previously mentioned. Several universities now have the equipment to make these tests. What these tests will tell you is whether or not these elements are present. They will not tell you how to get them out of the rock and its salable form. A researcher who has the money or the equipment for this kind of testing obviously has a far greater knowledge than I, so any help I may be able to give another, we'll have to be of a similar nature.
Again, a brief summary of the nature of the problem is in order. First, the metals in the ore do not fire assay. To have a product we must extract the elements in a form in which they will assay.
We have two choices. Pre-treat the ore so it will assay before extraction, or extract the non assayable elements from the ore and treat them so they form a normal element.
Either method of approach to the problem must reduce the complexity of the compound, alter the electrical level, and change the oxidation state of the elements.
Pre-treat usually revolve around a change in the oxidation state by roasting, or electro-oxidizing the ore in wet slurry by electrical current.
Roasting to be successful must have flux combinations that offer an oxidizing effect, decomposition of the complex compound, and reforming of the element into new and simpler compounds of a stable nature. Needless to say, exploring these possibilities will require some work.
Electro-Oxidation methods offer a simpler approach with fewer variables to consider. Most of the work I had done has been along this line.
Introducing electrical energy into a molten mass or wet slurry of the ore has given the most consistent positive results. Whichever way the pre-treat is done, the treated ore must be processed for the extraction and refining of the precious metals.
The alteration of the electrical structure of the element has been found to occur during a physical or chemical change of the reacting media. In the molten state using the smelting method, the change occurs during the melting or the cooling and crystallization of the melt media. In electrical arc smelting, the passage of a current through the molten mass aids in the altercation of the elements.
Toward this end was a method developed consisting of an electrical arc smelt using lead as a collector, and electrolytic separation of the precious metals from the lead. The procedure is called a recycle method as the cathode lead and the slags are remelted in a closed circuit.
The anode muds from the electrolytic separations are refined for the precious metals.
The wet method of treatment involves electro-oxidation of the ore as a pretreatment, and recovery of the values by leaching of the ore in a suitable solution. The filtered solutions may be electrolyzed, run through resin columns, or precipitated depending on the type of ore and the leach solution used.
These are generalizations, but each has its own characteristics, and the method must be matched to the ore as all ores will not respond to any one method.
From the various types of ore, let us first consider the black sands. These sands are nature's concentrates of non-oxidized iron compounds that usually come from a granitic source. They are found all over the country wherever granite mantle rock intrusive occur.
These black sands do not usually contain free gold. Where it does it is easily removed and will not here be further considered. Gold locked up in the sand iron is the target. There are usually magnetic and non-magnetic sands together. The first step is to magnetically separate the two fractions. The values may be in either or in both fractions.
Since the contained elements are in compounds on the molecular level, simple grinding fine is unlikely to produce the gold in a crystalline state that may be recovered by normal extraction method. The finest possible from a practical cost basis is necessary. The smaller the rock particles the more available the element becomes to be affected by further pre-treatments and final recovery.
Where black sands have free gold present, they will often yield values by find grinding with suitable chemical. The simplest is using an oxidizer and a detergent, followed by amalgamation. It is not unusual to recover from 10 to 30 oz of gold per ton from sands using this method.
The above will recover mostly gold. To recover a greater amount of silver and the Platinum Group metals, the following should be used. First, fine grind the sand in a hypochlorite solution. Decant and filter the solids. Dry and roast the ground sand in a suitable oxidizer at about 1500 degrees Fahrenheit. Amalgamation or wet leaches can be used for partial recovery at this point. Smelt the roasted sand in an arc furnace using lead or copper as a collector to a temperature of 2800 to 3000 degrees Fahrenheit.
The iron will be reduced to iron metal and will give up a great deal of the contained values to the collector. The iron should be poured into an anode bar by melting in an induction furnace. The iron bars should be broken down in a dilute solution of hydrochloric acid. If lead is used as a collector the bars may be reduced in Floroborate or dilute nitric acid solution. Values will be recovered from the resultant anode muds. The anode mud is to be treated by the recycle method as mentioned above for the best yield of product. Another source of the non-assayable ores is the shales or schists. A number of these deposits are now being exploited. The way in which these are being treated is not likely to recover the full potential of the non-assayable fraction. Some of the shales in Alaska, the Riggins schists in Idaho, the Mancos shale in Utah, and the Cle Elum schists in Washington I have run tests on many of these materials. Most of them gave significant amounts of the Platinum Group metals. Most of my research has been done on the Washington ores.
Since even a brief outline of the past thirty years of work in testing procedures for the Taneum ore would be too lengthy for the journal. While true iron ores are less abundant than other ores containing portions of iron or iron sulfides, they are interesting for the high-value some of them contain in all of the precious metals. I speak specifically of the heavy non-oxidized iron deposit. I have no experience with iron ores in the east.
If you have an ore that you believe has non-assessable what can you do to find if it is true? I would suggest that you test them as follows. This is the general approach I make to testing a new material.
First, find grind ore - 400 mesh. This is necessary to reduce the material to the finest possible particles to make the element available for further treatment. The grind maybe wet or dry, ball or impact, as long as the ore is reduced to the smallest practical size.
Second, make a series of acid digestions of the ore to reduce the element compounds that have the precious metals entrapped. Take a 30 or 60 gram sample and digested in hot acid solution using HCL, HNO3, and H2S04 or combination of the above. Use a 10 to 20% solution. Boil and continue to add acid until the reaction stops. Decant the solution and filter.
Precipitate the solution as a hydroxide. Filter and dry the precepts. Keep the solution. Fire assay the ore residue and dried precips. Assuming that you have assayed the raw ore, a comparison of the assay of the treated and raw ore should prove interesting.
If any positive results are obtained, go back to the saved solution from the hydroxide precipitate. This should be basic at pH 8 to 12, add HCL until the solution is pH 3 to 4.
The solution should be clear now. Add NaBH4 made up in a basic solution to the ph 3-4 solution. If a black precipitate is formed, this should be filtered, dried and fire assayed. Most of the Platinum metals and some gold will be found in this fraction if they are in the ore in a normal state.
Most of the gold and silver values will be found in the hydroxide precips. The highest gold values usually will be found in the HCL, especially if a sulphides ore is tested. The highest values in silver are usually found in the Nitric leach.
If these tests are repeated five times in the assays show different levels of results, you can be sure that the non assayable metals are present. If the total values average within 10 or 20%, you probably have a normal element or and it must be evaluated as such. If any wild reactions were wild differences in values are found, you can go to the next step. Follow the above procedures but place the sample in a beaker where it can be heated and agitated. An electrical current is passed through the solution. Carbon rods are used for anode and cathode. Current may be AC or DC at 6 to 12 volts. Try both. Keep the solution below the point of boiling to prevent excessive solution loss. Time is a factor in these tests and should start from 6 to 12 hours of digest and treatment time. The purpose of this treatment is not simply dissolution of the ore, but to add the effect of the electrical energy and the change in the oxidation state, to effect stabilization of the elements. This is a form of Electro-oxidation and is not an uncommon practice.
Depending on the ore in test, many different kinds of chemicals change my work on your ore. Hypochlorite and basic solutions may also be used.
Electro oxidation can be effective on many kinds of sulfide and pyritic type ores. A solution of HCL is added, because chlorides will reduce the sulphides. The iron is taken into solution and the sulfur will remain as elemental sulfur. Most of the non assayable values will go into the iron and maybe precipitated with the base metals. How the material is to be treated from this point will depend on the nature and the state of the contained elements.
As previously mentioned much of my research effort has been devoted to the Cle Elum schists or the Taneum or as it is common called. This material has a high degree concentration of the non-assayable precious metals. In The raw state it has a very little. At least fifty ways of treating the material have been tried. Almost every method will give positive results part of the time. None has been found to give High results every time.
A strict control of test conditions is necessary. The equipment required to maintain strict control of test conditions is very expensive. I have been unable to obtain funding to get the necessary equipment.
I presently have in operation pilot plant equipment for treating the ore with an electric smelt on the recycle procedure. By this method running 100 lb of or per day, I'm able to recover 7 oz of gold per ton of ore and 100 oz of silver.
However the positive result is that is in the proof of the values can be recovered. It remains for someone else to figure out a way to do the job cheaper.
Other wet methods as described above have at times given exceptionally high values from the Taneum. The electro oxidation of the ore has many times given values and silver over three hundred(300) ounces per ton, and a number of times over one thousand(1000) ounces. When the reaction triggers the silver, very little gold is recovered. When the action triggers the gold, a small amount of silver is recovered. The gold reaction has been found to be triggered by a low temperature sulfuric acid roast. Recent tests indicate that values in excess of 100 oz of gold per ton is feasible with the proper control conditions.
In the smelting recycle procedure, the platinum group metals show up in the third cycle of the refining procedure. Very little indication of them is found in the direct pre- treatment of the material.
A number of years ago, during a pilot plant test a procedure on the Taneum, a 10-lb dore bar was sent to the Handy and Harmon refinery. When refined, we were paid for the 2 percent platinum and 4 percent palladium in the bar, obviously showing a considerable platinum content in that Taneum material.
The platinum group metals are involved in the problems of the non-assayable. They are a part of but not the cause of the basic problem.
So, the non assayable ores for all practical purposes, are limitless in quantity. Many people are now working on extraction methods, any number of them are reported to be successful. Public knowledge of the limitless amounts of precious metals that is available with no doubt an effect on the marketplace. However, supply and demand factors will still function and the large-scale correction of gold and platinum from the non-assayable ores will no doubt require considerable time to achieve. For my part, time and money have contributed to induce me to retire from the pursuit of the non assayable enigma. To any person or company involved in the non assayable research, I will provide the information that has accumulated from the past years of work.
