TODAYS SILVER TEST

[Frank D.]

TODAY'S SILVER TEST

I did a silver test not long ago, and it came out a little bit milky, but nothing like this one I did today with a new suspect ore. Very thick frothy kinda suds on the top. I am wondering if it means higher grade silver in this ore? Has anyone did silver testing from crushed up hard rock and had these results?

 

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[Frank D.]

I just checked on it again, and now it looks like cottage cheese floating around just beneath the surface. ??

 

[timberjack]

What are you testing it with?

 

[Goodyguy]

If you did the test properly with nitric and hydrochloric acid a resulting thick curdy mass is an indicator of high grade silver.
The previous milky result was an indicator of low grade silver.

GG~

 

[Frank D.]

Thats what I wanted to check on to make sure Goodguy. Pretty sure I followed the directions, but at a little more amounts. One thing I did not do was heat it though. Instead I stirred the sample for a few minutes until the fluid turned blackish gray, and the only thing left in the bottom of the beaker was what appeared to be some powdered quartz. Maybe you can let me know what you think. Here is what I did. I added a half ounce of crushed to a powder ore to a mixture of two ounces chlorine free water, and one ounce of nitric acid. Stirred the mixture for three to four minutes until all but the quartz powder was dissolved,- Then I added a half ounce of muriatic acid. As from the photos above, it started bubbling, then foaming into a froth. There was some little white cottage cheese looking particles forming from the start, but after letting the stuff sit a bit, the acids cleared up to more the color of the muriatic acid, and there was alot more of the cottage cheese looking stuff in the acid. The ore I used for the test is a Phyllitic type with alot of quartz, I think chlorite, and under a jewler's loupe, I see alot of perfect shiny Pyrite cubes, copper, maybe gold with a high silver content, a silvery mineral I'm not sure about, and what looks like some magnetite. The thing that caught my eye with the ore, is over the surface in alot of the areas is a metal with a blackish coating. After scraping the coating off with a razorblade, I saw a metallic silver color underneath. It's not magnetic, and it's very thin, but covering alot of the ore. I picked up about 80 pounds of the ore and lugged it out in my backpack, and luckily the backpack didn't fail me! Still not sure how worth it this ore is or isn't, but next week my rock crusher will be put outside, and I'm gonna crush more of the stuff up, and run it. Also found some other type quartz in the same area with what looks like pyrargyrite spread throughout it. Some is ruby red, and some looks black until I look at it under my loupe in good lighting. Not getting my hopes up too much though. Thats why I'm here asking for advice from guys like you with experiance

 

[Frank D.]

Hey timberjack, see my reply above, and let me know what you think. Thanks, Jay

 

[Goodyguy]

If it were me I would crush up a pound of the ore that tested positive for high grade silver and send it off to be assayed to get an accurate reading of just what and how much precious metal is involved.

Personally I'm only interested in gold because that's what I know best. When it comes to silver I'm just not excited about it unless of course the quantity would justify the cost of extraction. If it's locked up in sulfides it's going to be expensive to recover commercially.

Heating up the ore will tell you if sulphur is present due to the odor that will be released.

GG~

 

[Frank D.]

It's definately sulfur bearing. I could smell it after I struck it with my mini sledge hammer. Just not sure yet if there is any value making it worth my time. Gonna crush some up next week with my rock crusher, classify it down and run it through my blue bowl. I did run about 4 table spoons of the stuff through the bowl and found alot of tiny pyrite cubes, and some sort of heavy green mineral. I guess possibly related to copper which would make sense since some of the rock has visible copper of tiny size. What I am trying to figure out, is these small iron, gold, and copper looking stains on the surface. Looking at it under the loupe, the gold colored ones actually look like gold. Not super shiny like pyrite. More like a warm glowing gold color. The copper ones look the same. A copper gold look to them. Very tiny though, but they are throughout the layers of the shale-slate Phyllitic looking stuff

 

[aussco999]

Hey Jayrock:

It looks like you need a little help testing your ore for silver. Goodyguy has you heading in the right direction, but your testing procedure is still to flawed to give any accurate results. I don't know your chemistry skill level, so I'll try to explain things briefly and in layman terms. For the most part, you will be able to use a batch receipt (equal in parts or volume) to leach the ore. I'll rely on your common sense to keep you safe. This info is somewhat more labor intensive and as GG said, you could send it out for assaying, but what the heck, that's no fun.

Direct testing ore for silver is a bit more complicated as there are about 58 other minerals/metals that are also soluble in a nitric acid leach and most all of them will go into solution before silver. These other minerals can and will cause a high consumption of nitric acid and may give you a false/positive reading. Also, the milky precipitant you might see after chlorination is not definitive for silver as lead (Pb), mercury (Hg) and thallium (Tl) will appear milky too. The only way to rid your ore of this interference is with some form of a pretreatment process.

Because the effort is about the same, it benefits you to do both a quantitative and qualitative testing when possible. This basically means starting with a dry ore and measuring accurately. Also, unless you have access to equipment that measure in ppm/ppb, then you need to work with samples large enough to see the visible results. This can normally be done with a 1 to 20 lbs. ore sample. You can do a direct conversion to oz/ton with a 2 lbs ore sample.

No leach is effective unless it's in contact with what you are trying to extract, so pulverizing to liberation is important. Chemist, Dr. Powell of Johnson Matthy has determined that, “not less then 12% (1:7 nitric acid to distilled water) nor more than 15% of nitric acid would be needed to leach sulfur/sulfosalts from ore”. I've found the 15% ratio works best on sulfide ores. Cover the pulp with 3 to 5 times it's volume with the nitric acid leach.

Heating the leach is not needed and may cause problems with sulfide ores. If the leach temperature exceeds about 95 F, sulfur changes to a black (alpha to beta) rubbery like material and causes a surface coating. Be careful of rising temperatures from any exothermic reaction when adding the acid. Ambient room temperature works best and allows you to use plastic buckets for leaching.

Allow 16 to 24 hours for this pre-leach to work, with occasional stirring, then filter off the liquid and wash the pulp twice with clean water. Mr. Coffee filters work great. If you are still seeing sulfides in the ore, repeat this process as many times as needed.

Now you are ready to leach metals from the pulp.

So that this post doesn't turn into a book, I'll stop here for now. Let me know if you want to continue with this process as I should be around most of this week and will post the remaining info. Depending on the economical value of your ore, this may turn into another 2 or 3 part long winded post.

Good luck with your project.

John

 

[Frank D.]

Hey John, that is some great information, and I thank you for it. Yes, I'm not sure what the hell I'm doing because this is all new to me and thats why I'm here. To learn. I would love to have the full details of what I need to do to get proper results. Even if the test turns out to be a wash, it would be great to have the knowledge to successfully do the test whenever I want, and without bugging everyone all the time! Thanks, Jay

 

[ecmjamsit]

The only true test for silver is a fire assay. Crush the ore to a powder, add litharge and flux. Fire it up in a crucible, pour out the molten charge. Clean off the slag, and cupel the remains. I have done it a few times...try google "fire assay"


http://www.lornet.com/prospector/articles/assaying_fire_assay_procedure.htm

 

[jair]

The only true test for silver is a fire assay. Crush the ore to a powder, add litharge and flux. Fire it up in a crucible, pour out the molten charge. Clean off the slag, and cupel the remains. I have done it a few times...try google "fire assay" http://www.lornet.com/prospector/articles/assaying_fire_assay_procedure.htm

this is the way I assay , for gold I use a kiln that goes to 2300 degrees . I'm sure not every one has one .

 

[Frank D.]

I am getting a torch shortly, so I could try that. Thanks

 

[Frank D.]

I wish I had a kiln. I have seen them decently priced used, and may get one.

 

[Real de Tayopa Tropical Tramp]

Jay rock check on making your own, both electrical and gas powered ones work just fine. I have had to build both while working as an assayer. The torch works just fine also if you adjust your flame' s action, oxidizing or reducing..

In fact up at the colorados, all of the equipment had been destroyed,or stolen, so I had to make my own - this included remaking the electronic balance and recalibrating it, making my own cupel mould and cupels, even made them with 25% cement due to a shortage of cow skeletons..Actually I had fun, even to overhauling the Perkins AA which had been deliberately sabotaged I can still see the boss's face when he entered the lab and saw his prized AA in pieces, it wasn't working anyways Did after.

I too, am looking forward to reading more from Auss -john.

Seriously if you have any questions just em or post them. Remember the old Spanish miner just leaped off of his mule or burro and proceeded to assay and mine with just what he could make with just local materiel. You can do far better thanks to your local building materiel supply business.


Don Jose de La Mancha.

 

[aussco999]

Hey Jayrock:

I was trying to get back with a quick response, but work has interfered again. You've got the right attitude about learning and this is a good place to add to your education. My “full details” come from a large reference library, a lot of work in the lab and several years of mining projects in a country that specializes in silver exploitation. But, this will be more like a “Cliff Notes” version on silver ore treatments.

Most silver mined today are from sulfide ores such as argentite (acanthite) and pretreatment to remove the sulfides will include; roasting, chemical and aerobic bacteria leaching. Each method has it's pros and cons, but they are all are economically viable for commercial applications.

Roasting (oxidizing) is fast, but has higher start up costs for equipment and environmental concerns. Bacteria is cheap and can be done in any batch/vat/heap leach, but may require a finer grind size, has a slower reaction time and is effected by temperature. Chemical treatment is often done the same way using sulfuric acid to recover base metals, even producing more sulfuric acid. It's not as slow as bacteria, but may require a pH change to leach the precious metals.

Unlike HCl and sulfuric (which are considered reducing acids), nitric acid is an oxidizer and not normally used on a commercial leach level as it's to expensive, easily neutralized by carbonates and produces some toxic byproducts, but it's great for analytical testing. The most aggressive nitric acid formula for leaching silver is 1:1 (acid to water), no heat needed for ore testing. Scrap metal testing and extraction is another story.

Your top photos look more like effervescence (frothy bubbles) caused by the nitric acid being neutralized by some form of alkali/carbonate material in the ore. The milky white precipitant you are looking for will be in the leach liquid, not on top. Here is an animated GIF link to show you what it should look like;

http://www.chem.uiuc.edu/clcwebsite/AgCl.gif

A thin white milky precipitate indicates the possible presence of silver (or lead, mercury, etc), but probably not in an economical amount. What you're really looking for is a large volume of curdled cottage cheese precipitant.

Here's the nitric acid extraction process;

After ore pretreatment to eliminate sulfides and other gangue material, place a 2 lbs sample in a large glass or plastic container. Cover the sample with about 1 pint of deionized water. Slowly pour in about one-half pint of nitric acid, stir and allow any violent reaction to settle for about 15 minutes. When reaction stops, slowly pour in another one-half pint of nitric acid (equals the 1:1 ratio). Stir occasionally and let set for a couple of hours at room temperature. Everything that's soluble in nitric acid will now be in solution.

After settling, decant off the liquid and filter the pulp with 1 volume of water, then discard the pulp. Now you are ready to chlorinate the liquid. This can be done by slowly adding HCl acid or directly with deionized salt. You're looking for that high value cottage cheese at this point. Also, the color of your filtered liquid might give you a better idea of some of the other contaminates in the ore.

For example; if murky, antimony and/or bismuth are present and precipitating. Violet to purple is manganese. Yellow or orange is iron. Blue or green is copper, and swamp-water gray or black is a combination of all the above.

That's enough info for now. Let us know the results of your pretreatment and nitric leach when you can. If you have the good cottage cheese stuff, I'll post an easy and simple method to convert the chlorides to metallic silver.

Good luck,

John

 

[Frank D.]

Thanks for the great info. here John. I have been studying up on the different sulfide minerals, Tellurides, ect. lately because that is the type of deposit I found (sulfide). I have read that some have a high precious metal content. My issue is the accuracy of information I am finding on sites like Mindat, webminerals, ect. While alot of the information is consistantly the same, on some of the tellurides, ect. the physical properties descriptions are different for some. I am just assuming they are both from the authors personal experiance of finding and successfully testing the minerals for a positive ID, but colors can vary from geographical locations? I know I have found galena, copper, and Pyrite in the ores so far, but there are at least six other types of metal associated minerals going on. All of them are brittle, and from what I have read so far, those are the ones I would want to find. I tried the bacteria method and did see some type of results, but not sure. I kept the stuff (very rusty textured nail shaped pieces) and am gonna test it soon. That info. you posted is definately the most understandable yet that I have read. I thank you for that, and will try it out. If I was to post some pics of the ore that I have, would you possibly be able to ID some of what I have? Thanks John, Jay

 

[gold tramp]

Always do a fire assay, as to first make sure you have PMs that can be recovered, I believe big mining uses fire assay when on the hunt for metals as this is tried n true method of figuring out exactly what you have.
Theres is an old saying if you can cupel it, you can sell it.

chemical process you all are discussing I beleive is more for pregnant leach solutions ?
GT......

 

[aussco999]

Hey Jayrock;

This post is getting a little side tracked from silver ore testing, but everyone's enthusiasm for what you're doing is encouraging. Unfortunately, some of the advise puts the cart before the horse, as I don't think you need to buy an assay kiln at this time. Fire assaying is a different science than wet chemistry, and it's still cheaper to send samples out for third-party verification. For less than $150. you can get a gold/silver fire assay, plus a 50+ element ICP mass-spec analysis done. The mass-spec may also help identify the other mystery metals in your ore. An assay will give you a quick answer, but not as much fun as doing simple field tests.

(NOTE: If you're still interested in getting involved in fire assaying, get a copy of “A Textbook of Fire Assaying” by Edward Bugbee. It's well written and easy to understand. When you get comfortable with that info, I can probably help you with a customize flux receipt for your specific mineral).

When trying to ID minerals yourself, getting back to basics is the fun part of your education. With a minimum of equipment like an eye loupe or microscope you can determine crystal structure, some unglazed tile for a streak test, a few household items for the hardness test, a big hammer to fracture, a few chemicals to get a reaction, a balance to check specific gravity and a torch to do blowpipe or plaster tablet tests. Then, neither the fun or the confusion will ever end.

A mineral photo means little to me as I like the “touchy/feely” method for identification (besides, I have a complete lab at my disposal). My geologist friend always says “if you can't get up close and personal, then it's just a wild-eye guess”. When we are seriously looking at a mining project and spending a pile of someone's money, he will only do the hands-on stuff.

You've mentioned tellurides a couple times as it's often associated with gold and silver, but not always a guarantee. Tellurium ores are about as rare as platinum ores and can be visually ID in the field with chemicals and a blowpipe/plaster tablet torch test. There's not that many places in the world where tellurium is mined for precious metals, but maybe you've found the next big one.

I know we are just sideline chatting while you are waiting on the leach results, but let me know if I can post more info on that subject.

As always, good luck with your project,

John

 

[Frank D.]

Hey John,
Thanks for your advice once again John. It is much appreciated. Currently I can't afford to get an assay done on the ores I am suspicious of. The little bit of equipment (rock crusher,slate table, and blue bowl) I have this far I made myself for next to nothing except a 28.00 plastic sluice I bought from ebay. So a fire assay is not in my near future unfortunately. Since I am almost set up in my backyard, my plan is to seperate, crush, classify , run, and label all the heavies I get from each different type of ore (3 kinds). From what I have read, even gold that is locked up in sulfides, ect. still is around 8 times heavier than water, so what I believe, is as long as I pay good attention to classifying, I should catch anything of interest in the sluice, and for safety reasons, I will have a catch pan just in case the plan doesnt work, at least I wouldn't of lost anything. I recently have found some free mill gold, but it is very thin, and unless there is a whole bunch more, it won't add up to much in weight. Once I get a good amount of heavies, I will examine them, and will make a decision on where to go next depending. Even if I find more free mill type, I still may decide to do an aqua regia test. I say that because you hear me mentioning Tellurides quite a bit, and I understand that they are very rare, and I most likely am not looking at that. But what peaks my interest is the fact that whatever this highly shiny silverish mineral is, it behaves just like gold does. Just for a test, I ran some unclassified material with this silverish stuff in it. I adjusted the water flow to an extreme amount to move the 1/8 inch sized material, and since the sluice is two feet long, I set it at a two inch drop. As I added the unclassified material, the water flow was blowing the largest stuff right down and out of the sluice. And the very tiny particle sized silverish metal didn't even move. I kept adding material at a fast pace to try to disrupt the stuff, and get it into the first riffle, but it wouldn't budge. So I looked at some of the bigger (tiny grain) sized stuff under the loupe, and it looks like the crystalline gold structure, but like I said, it's a very bright silverish shiny metallic looking mineral, and it's fracture is brittle since I tried the hardness test on it with a hammer. I am not dead set in what it may be, so if you may have any ideas to steer me into learning more, and figuring this out, that would be awesome. What I do know? It's super dense with a shiny silver color, a metallic luster, non magnetic, and brittle. The pieces are too small for a streak test, or I would of done that. I think I'm gonna take a sample of the heavies, roast them to burn off the sulphur, ect., than do an aqua regia test on it. And if I happen to drop anything out of that, than I'll heat it up, cool it off, and hammer the small sample as thin as I can, the put it in nitric and see what if anything, is left over. What do you think? I already have all this stuff, so I don't even have to spend money I don't have. Thanks, for the advice, and I'm looking forward to more. Jay