tough ore to crack

[eemtek]

have some ore that came from mexico. My friend thought it was silver, but all the tests say "no".. I used my jaw crusher on it, then ground it down to powder. ran it though the shaker table and thought we were going to be millionaires. The metal looked great with silver powder and gold powder that ran to the collector. There was nothing magnetic in it. now the fun part.

I ran it through nitric acid to separate the silver from the gold.. Something dissolved, but not much.. I tried a little hcl to drop some silver with no luck.. I tried the nitric acid again, but no reaction. so, no silver?

So now for the AR, I put ar into the solution and got some reaction but not much, so I brought it to boil. It boiled til the solution was dead, but it tested for no gold or pgms. I even watered it down checking for silver or lead with nothing. so, I ran a 2nd solution on the metals and nothing happened even under boiling..

so, I dried it and weighed it to find only 1/4 of the original weight was dissolved. the metal left looks like fools gold and some silver, but it is not magnetic, and under the scope it has soft edges.

I took an ounce of it and added borax, soda ash, and sodium nitrate and made a metal bead that smells like sulfur and looks black.

my question now, what would be a good way to find what it is either by chemical or smelting? now I just want to know what i have?

I've work with local ores for years, but I've spent a week on this with no results. Makes me feel like a noob :roll:

 

[Harold_V]

Have you given thought to crushing a small sample, then roasting, to eliminate sulfur? Once that's done, you may have some degree of success with acids.

I've processed gold bearing pyrite that way with good results. In my case, the ore was roasted, given a wash in HCl, then roasted again, followed by another wash in HCl. My purpose was to eliminate, totally, all sulfur. You'll be surprised how much is left behind after the first roasting.

Do this with a fume hood, or outdoors, with a good breeze. Rabble the material as it roasts, to expose all to atmosphere. Heat to a dull red heat.

Harold

 

[eemtek]

always thought nitric would oxidize the sulfur and strip the metal. it would be a waste of acid, but good just to test the metals. but I will do a roasting tomorrow. If that is the problem, then i'm going to have to move operations elsewhere, I dont want the sulfur smell around the house if Im going to do large batches..

any ideas for roasting large batches of ore, say 500-2000 lbs at a time? My friend was told it should hold 20lbs of silver or more per ton with 100-180 grams per ton of gold.. he wants me to see if it is true, so he sent me 500lbs.. You can see the silver balls throughtout the ore, but you can smell the sulfur.. so far, I've had no luck.. maybe if i roast the whole ore after I ball it, more metals will surface?

 

[Harold_V]

I'm not sure you're going to enjoy roasting a large volume of this stuff. You'll fill a neighborhood with SO2, and very quickly. You may also have arsenic present.

With the cost of energy these days, plus EPA breathing down everyone's neck, I expect this isn't a good thing for you to process. I had but a couple of 5 gallon buckets of already crushed pyrite to roast, and it took considerable time. I used a sheet of stainless steel (1/8" thick) on top of my small melting furnace. Did the actual roasting under my melting hood, so I didn't have to deal with the resulting SO2. Do keep in mind, this was before we had so much environmental control----what I did then would likely draw considerable interest today.

To my knowledge, nitric doesn't deal with the sulfur. The HCl process I used was to dissolve the liberated iron (oxide), which it did very nicely. While I don't recall the particulars, the two 5 gallon buckets were reduced to roughly a quart of material after three iterations of roasting/digesting with HCl. From that quart I recovered what I recall to be about six ounces of gold.

Armed with the above information, I don't think I'd get involved with the ore you speak of, even at gun point. It might be a fun thing to experiment with, though.

Upon re-reading your post, the numbers are impressive---but you'd be best served to pay for a fire assay if you have the slightest intention of getting involved with this ore.

Harold

 

[eemtek]

I've been telling them I want to send out for a good assay. I was thinking david fell, but dont know if they are good with ore? I was going to process this batch, but you are right, i dont want to do the roasting.. I was thinking they could grind it and send it to me.. I have a couple recovery machines I could gravity seperate the metals, then treat them.. I am averaging 3oz of metals per every 2lbs of ore, but this has considerable sulfur the more i look at it.. too bad fools gold in a bottle wasnt worth much, it just looks good as it is.

going to roast a small batch tomorrow and see what i find.. maybe if it is what they say, I can have them roast it at his yard in mexico before they bring it up here. They have no problems using mercury down there. They showed me how they used mercury in a drum and use bare feet to mix the enriched ore with the mercury to recover the gold.. I've showed them the hazards and diseased it will cause, but they dont care? Maybe this will be the lesser of evils? I do know they have a hard time getting the rock across the border, I could only imaging about semi white powder

thanks for your input.. I'm just glad i dont have to deal with sulfur in the ore i play with.. I usually collect rocks and crush them down from around 1100 lbs to around 70lbs of blacksands that I just run a cyanide leach through in a 5 gallon bucket with holes and a filter in the bottom. I only use a couple gallons of solution and recover the values at different times over a couple weeks. I use the same solution and just recharge it so i dont have and chemical waste. I thought my method would work on this new ore, but dare not even try with all that sulfur.. I'd just waste too much cyanide and spoil the solution.

thanks for giving me a new idea, I should have done it in the first place, but i thought my chemical method was just as good on a small batch.. I was even thinking about ozone in a hot aqueous solution, but dont think that would help either.. I just know i am out of this job unless there was a way to get rid of the sulfur before it came to my place.. thank you Harold for your input...

 

[nickvc]

We have Rick the Rockman as a member here on the forum, if you look for his threads he also does assays and is very knowledgable about ores generally, it might be worth talking to him.

 

[Harold_V]

Your mention of cyanide is interesting.
One of the things I tried was to extract the values I spoke of, using my agitation tank. This was before I built my filter press, so I got baptism by fire. I'd pull a sample of the solution from the tank, then I'd filter immediately to run a test. Sure enough, I'd recover gold. I'd then allow the contents to settle (still in the tank), then siphon off the cyanide solution for precipitation.

Nothing!

I came to understand that while I was apparently dissolving some of the values, the time it sat idle allowed it to precipitate. Why, I have no idea, but it became apparent to me that I was not going to enjoy success with cyanide. Only after considerable thought (and reading old books on processing ores) did I conclude I'd have to roast.

Pretty much all I've learned has come the hard way. Failures tend to be very good learning experiences. of which I had my share.

A comment on the "white powder". It won't be. If my experience is meaningful (it may not be because of different ore), after roasting the ore was pretty dark, bordering on being black. Still, it might be hard to explain to those that may not understand exactly what is being transported.

Harold