jan,
Nickvc, and 4metals give very good advice pay close attention to it.
I am not a professional miner, or any kind of expert on anything, and as you know recovery of these metals from ore can be difficult, there can be several approaches and you may have to experiment with different methods to find the best approach.
At this point we really still do not have enough information to make a decision of which way to go, and in the end you will be the one to make this decision by what you find when dealing with your ore.
From your description:
Ag 10.73, Pd 11.62, Rh 14.34, Ru 7.67, Pt 2.58,Fe 54.80.
I do not see mention of Iridium doesn’t malanite contain this? There are probably many more metals involved like cobalt, nickel and who knows what, like arsenic or mercury or some other metals that may pose dangers in the processes or become problems with certain processes, a good assay can help you to make the decision of what way may be better to try and what to be careful of.
Besides iron and the free gold you seem to be reclaiming, you seem to have a fairly high content of PGM along with silver, in a sulfide ore.
You are grinding the ore in a ball mill, screen, and removing the iron with magnet, concentrating with a centrifuge to recover free gold and heavy material.
You did not go into details of what your process is with this more valuable material (please give more detail here).
We will look at silver more later, in this post,
Here your process sounds good, I would also check the iron removed with the magnet for values.
The concentrated material is should be where the main value is, these are sulfide minerals high in sulfur and PGM like I said I am no professional and only play miner as a hobby, but from what I can tell the possible metals in the ores you listed are Pt, Pd, Ir, Ru, high in sulfides. You also mention recovery of free gold (so I would also assume there to be gold locked up in the iron sulfide\ore also.
Valuable sulfide can be froth floated in oils and air as a recovery method, if using this method you would want to concentrate them as sulfide before roasting, silver sulfide can also be concentrated using this method as well as gold.
Roasting to drive off the sulfur and sulfide, this is important before leaching, elemental iron metal added to this roast can be beneficial, as the iron metal will collect the sulfide and release the valuable metals bond with sulfur, possibly releasing gold silver and PGM's, once the sulfide is removed the iron in the roast can also give these metals back an electron the sulfide had when it was bonded to them, and convert them back to elemental valuable metal powders, the heat and air will drive off SO2 gas as the sulfur burns adding fuel to the roast, and as the sulfide’s are heated iron collects the sulfide (from the valuable metal powders in the ore), and releases it as SO2 gas as the iron forms oxides of iron in the oxygen rich environment, oxygen is also beneficial here, good exposure of powders to air by stirring and raking of the red hot ore, not only will help to remove sulfides but also help to oxidize the base metals which are much easier to oxidize than the more valuable more noble metals, this will help when leaching and removing base metal from the more valuable metals in a leach process later, depending on choice of process.
Sometimes salting the ore in the roast is beneficial other times it may cause trouble, salt NaCl in a roast sometimes can help to form chlorides in the roast, making a chloride leach later more easy, but if too much salt is used or the chemistry of the ore is such that this method would not be combatable, you can also make values more volatile and lose values in fumes, and could fume off values in a valuable chloride gas leaving the roast. (With your ore I would not try this method).
Now that we have this concentrated material roasted we can more easily remove the oxidized base metals and as our valuables will be mostly elemental metal powders at this point, and most of the other base metals are oxidized, some of the non magnetic iron may become magnetic (caution collecting iron with a magnet can also pick up some values so check this material later), many of the valuable powders may also be more easily separated from the oxidized base metal powders using water and gravity methods (maybe experiment with gravity separation again at this point and see if there is any benefit, water may also help to remove some of the more soluble oxides here, and the powders no longer being sulfide salts of metals but elemental valuable metal powder and lighter base metal oxides, you may find it beneficial to use gravity again.
Now to separate base metals further from the oxidized base metals, choosing or experimenting with which leach to use for the base metal leach is important, or if we are using a leach more selective for values, you probably have access or experience with chemicals that I do not have access or experience with, but if you discuss your methods, there are members here that may help.
Also depending on how well we can separate the base metal from the valuable ore can also determine what method of further recovery or refining or separation of these valuable metals we may try.
With high PGM content I tend to think smelting the PGM and gold, with silver metal as a collector is a good idea.
Your silver ore can also be used here, and recovered also, (your silver sulfide ore that was converted to elemental silver metal powder in the roast with elemental iron as described above, it could be used as the roasted powders, or if you can get a good separation of the silver powders after the roast, melting the silver powders with elemental iron metal, you could get silver metal silver which will not alloy with iron (like gold will),and any unconverted silver sulfide left after roasting would convert to silver metal in the melt, again iron taking the remaining sulfide and forming SO2 gas, the iron oxide reporting to the glass slag from flux) this silver could now be used as a collector.
Depending on how much silver you used as a collector to the amount of platinum or platinum group and gold in the ore, can make a big difference in how these would react to some acids later, or if you used enough silver to make very high silver percentage of silver anode, the PGM and gold could be collected in an electro-refining cell as anode mud’s as you recovered silver in the cell, then you could further treat the anode slime for recovery separation or refining of gold and the platinum group or selling to a refiner.
Like I said mining is not easy and there can be several ways to go some ways will get you there, some ways you could just get lost, and other ways would get you to where your going faster and better, also you may have to experiment on which way works better than others with small experiments before you commit to which direction you will go in this journey, there are many members here on the forum more experienced than I am, I only play with mining on a very small scale, but I am sure the forum can help you in some way to come up with a method that will work for you, we could use more details of how you are processing and maybe we can give you a few more ideas, to decide which direction you wish to try.
You will find reading Hokes book and the forum very beneficial in helping you develop and improve your processes.
