Dukes/Maulsby Question - Silver #52

[jobinyt]

I've found a small lead/silver sulfide vein/stringer system identified as such by test 52.

I'm curious, can I use the below (or some modification you suggest) subset and slightly modified version of test 52 to do a quantitative analysis?


TEST No. 52: Silver - Ag. Page 1 of 3

TEST A: In dilute nitric acid; precipitated by as chloride.

1. Use powdered mineral (or concentrates) size navy bean. (I'd use an accurately weighed amount, and adjust fluid amounts given below according to sample size. It seems to me, my result might be improved by roasting the sample after weighing and before proceeding)
2. Place in test tube with 1 cc nitric acid; 2 cc water. (Water must be free of
chlorine - See Test 50)
3. Boil for some considerable time to dissolve the silver.
4. Filter; let set until cold.
5. Re-grind filtered material and repeat steps 2-4 to ensure high rate of extraction - combine solutions. Repeat again, but this time add few drops of hydrochloric acid (or salt) to solution to confirm high rate of extraction. RESULTS: A. A white precipitate if silver (or lead). B. A milky or opal color if very low grade. C. A thick curdy mass if high grade. After high level of extraction is proven (ie, no milky color/precipitate from adding hydrochloric acid) proceed as follows:
6) Combine the filtered fluids.
7) Slowly add a few drops hydrochloric acid to solution and stir and settle until no more precipitate is formed. (Probably decant fluid and repeat to prove all precipitate formed)
9. Pour off as much liquid as possible without disturbing the precipitate in bottom
of tube.
10. Add 2 cc of water and heat to boiling.
RESULTS:
A. The lead chloride in the precipitate will dissolve.
B. The precipitate will contain silver chloride. What other metals would stay with the silver?

Confirm silver as follows:
11. Pour off water without disturbing precipitate.
12. Add 1 cc strong ammonia to precipitate. Shake tube slightly.
RESULTS: If silver, precipitate will now dissolve.
13. Add 2 cc of water.
14. Add 2 drops of nitric acid.
RESULTS: The silver will be re-precipitated. Question - is precipitate silver, silver nitrate, or silver chloride?)

15 Dry and weigh precipitate; calculate % silver (if nitrate/chloride); divide by starting sample weight to get percent silver in ore. Might there be anything else in the precipitate? If so what - I can run other of Dukes tests to see if such might be present in sufficient enough quantity to invalidate my rough assay.

Yes, I know this isn't a 'proper' assay. Still, I get the impression from running this quantitatively that there is quite a bit of silver in this ore. Having some idea if it's 2, 4,10, more % - and I'd do the same for the lead present - would give me some basis for experimenting/evaluating concentration techniques, and deciding if the prospect is worth more effort.

 

[Martijn]

(Probably decant fluid and repeat to prove all precipitate formed)

No you can let it settle and add a drop of HCL to see AgCl form. No need to decant. The AgNO3 will be throughout the solution so you if there is no white cloud formed by adding a drop of HCl, all silver is turned in AgCl.

 

[jobinyt]

Thanks Martijn. That's obvious - now that you pointed it out.

Hope I get comments on my other thoughts.

 

[goldshark]

Why not fire assay it?

 

[jobinyt]

Why not fire assay it?

Several reason, each sufficient on its own. First, I should perhaps say I already have all the required equipment and supplies - have run this test qualitatively.

1) For the fun of it - some sort of personal satisfaction - maybe a character fault but seems like fun to me.

2) I've got, roughly estimated, 700 pounds of the ore - pieces as large as 80 pounds. It's all quite heavy, but some is modified host rock, some pretty pure. There are roughly a dozen veins in one spot. It would take many fire assays to determine what is and isn't worth processing, and gathering more of; impractical I think.

3) Most of my prospecting is remote. North of 60 as they say. I find a fair amount of stuff that interests me, but as a practical matter would take me a year to return to if I relied on fire assays. If tests that produce precipitates can be used quantitatively, I think I'd be much more productive and knowledgeable.

 

[galenrog]

The purpose of the test you performed is strictly qualitative. To determine if there is silver in the sample.

The reason we perform field tests is to determine if further analysis, such as assays, are necessary.

Are your rocks worth processing? Only an assay will tell that story.

Time for more coffee.

 

[jobinyt]

galenrog - We think differently. 700 pounds times 14 oz/lb is about 10,000 ounces. A reasonable guess is 2-4% silver - could be, say, 10-15%. ANY way I look at that, it's hardly likely to be of interest to a commercial processor, and possible but unlikely of financial interest to me. The value here isn't in the ore I've collected. The value is in my fun, and learning. ​

No offense meant to anyone, and I can see an assay is often the 'smart' thing to do, but any dolt can buy an assay. I'm looking at this as a learning experience - not a money making opportunity. What distinguishes which parts of which veins have high silver content? What do they have in common and what differentiates them? In other days and other places, what can I do in the field for immediate results rather than waiting a year. Why a year, someone will ask. Because I'm only in the area in summers; it is a day hike in and out, and a 5 hour drive to the nearest place I could possibly find someone to do an assay and I'd need many assays, and probably followups for a proper learning experience. I'd much rather set up camp and spend a week there than spend so many hours - and days - hiking in and packing out. My questions are:, What might be the limitations/accuracy of the test I describe? Can it be improved for field use?

 

[goldshark]

Since I don't know how much experience you have with mineralogy, I will just throw this out. If you can identify the mineral, it will tell you the quantity of the elements in the mineral. Once the mineral is identified, base it on approximation of mineral to gangue ratio. That would give you only an approximation though, without going fire assay. I don't know if you have a blow pipe, and a guide for blow piping the mineral, but that can be a handy test also. This is a little safer than mixing some unidentified mineral with acids, if you have not 100% identified the mineral.

 

[jobinyt]

Apologies for the delayed response. I'm very interested in this topic, but was off on a short trip.

I know a little, but not nearly as much as I'd like. I have, and use, most of the tools appropriate to mineral identification: accurate scale, specific gravity tester, blow pipe, hardness picks, charcoal blocks, platinum wire, heat sources, assorted glass ware, assorted acids and chemicals, book on crystallography, Maulsby's book, and other references.

"identify the mineral, it will tell you the quantity of the elements in the mineral." Maybe, sometimes, but not in this case. The mineral is galena - lead sulfide. Galena is usually defined as PbS - lead sulfide. However, it is rarely found pure. There are many sulfides. Some definitions of galena is that it is at least 50% lead.

Now, let's look at acanthite - silver sulfide - AgS. Again, rarely pure and sometimes said to contain up to 50% other sulfides - often said to be lead.

If we look at sulfide minerals, there are quite a few, but looking at the Reactive Series of Metals we see there is only one between silver and lead. That one is copper. When I precipitate the lead, I also remove the more active elements such as antimony, arsenic, copper, molybdenum, zinc, more. It is not clear to me whether the copper follows the lead or silver. It is clear, the bulk/ore/samples I have contain lead and silver. I want to determine how much silver is present, and is it just in the 'galena' or also in the enriched adjacent rock.

Referring back to my original post. It seems to me I can extract all the silver (including perhaps any copper present) as described, and determine ounces of Ag (including copper) per ton. I've learned though that things aren't always as they seem to me. In this case before proceeding, I thought it good to check.

Something else interests me in this particular system. There is a small area of host rock that reminds me of Cobalt Ontario. I know of another area with evident sulfides and one old mine that contain veins of similar appearing rock. I've seen no sign of native silver, but the presence of nearby silver sulfides makes me wonder if I should be checking these too for silver. Again the costs and time delays in all this testing dissuade me from using classic assays at this stage.

 

[goldshark]

What is the host rock?