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Techniques for CollectorsIron Out Causing Green Stain

16th Aug 2016 11:51 UTCGary Moldovany

Lately, I have placed various minerals into Iron Out for rust removal. They have a green stain on them after 1 day in the solution. I have experienced this with quartz, analcime, scapolite and diopside. I'm wondering if it's something in our tap water? It's never happened before until recently. I wash the buckets out thoroughly before use. Iron removal is accomplished but now everything is stained green. Help!

16th Aug 2016 12:59 UTCAndrew Debnam 🌟

Hi Gary, Funny you should mention this (the stain is not funny) but I noticed these stains recently cleaning some Amphiboles. I use tap water as well. I reduced my soaking times ( 6 -8 hours) and rinsed my sample between soaks with light cleaning in soap. I then used fresh SIO for the next soak. This seems to have worked so far. I am not sure if it the tap water or perhaps the SIO degrading from the iron going into the solution. I have also taken more care in pre-cleaning the samples before the soak as well. So spray gun - soap - brushing etc.

Andrew

16th Aug 2016 13:07 UTCGary Moldovany

-- moved topic --

16th Aug 2016 13:34 UTCHarold Moritz 🌟 Expert

That happens to my stuff sometimes, I suspect the solution is converting the brown iron3+ to green iron2+ and not putting it into solution like it should, but I'm not a chemist...take the piece out and put in clean water and then dry and it mostly goes away.

16th Aug 2016 13:40 UTCBob Harman

Over many years I have used iron out on quartz and the simple sedimentary minerals in Indiana specimens. As I am sure you already know, some minerals survive rust removal quite well while others lose any luster and are dulled or have colored crusts, such as you mention, added to them or left on them.

My plan almost always calls for as short a soaking as possible to get some meaningful improvement in the specimen. A blanket overnight soaking or "1 day soaking", is in my opinion way too long for the vast numbers of MY specimens. Any soaking of this length will do more harm than good on most of MY specimens. Any soaking needed to be this long on a specimen OF MINE suggests to me that the example may not really be worth trying to meaningfully improve. But these are MY specimens and may not translate to yours. You have to be that judge.

Bottom line; shorter soaking times with repeat rinsings and repeat examination of the specimens to see the interim results as the iron out soaking continues. CHEERS.....BOB

16th Aug 2016 13:46 UTCMatt Courville

I generally use a toothbrush (avoid your washroom one if at all possible) beforehand to clean everything off. Even with long (days)soaks on some ugly coatings of amazonite I never noticed this myself? Perhaps try some distilled water or even some bottled water to see if you can rule-out your own tap water on a small discard piece. A photo might even help others figure-out the chemistry of what is going on. I know that from working in a lab, dissolved copper and nickel will show shades of blue and green - but this is more with stronger acids opposed to the 1-5% citric acid in the product.

Matt

16th Aug 2016 13:54 UTCHarold Moritz 🌟 Expert

The green I have encountered happens with feldspars and muscovite and not with all the pieces from the same pegmatite. I think it may have something to do with the chemical nature of the particular stain. The solution is not adding a stain, but converting the existing one. If you think it is your tap water, then save and use the water from your dehumidifier or air conditioner drain (they are really the same device). This is distilled water. But note that it will have a pH of around 6 and thus should not be used with calcite, etc. Silicates it should not be an issue. SIO is buffered though so it may not matter.

As Bob mentions, I generally agree that soaking as short as possible is important, especially for non-silicates. But I have found that quartz and primary silicates are unaffected by the long and repeated soaks needed for the tough stains commonly found on them. "Your results may vary"!

16th Aug 2016 13:59 UTCWayne Corwin

I too have had that problem a few times.

If I need to soak it for more than overnight (about 12 hrs) then I add some more SIO (a big spoon or 2) in the morning, and all seems ok.

Try a diffrent bucket, or try some distilled water maybe.

During the daytime soaks I like to leave the bucket where it gets sun all day, keeping it warm, that might help?

Let us know if any of these things help (tu)

16th Aug 2016 14:09 UTCBob Harman

And I should add that I am pragmatic about this. Long ago I have forgotten the college chemistry of all this. Besides, for me, it seems largely irrelevant. What is relevant and the important point is developing an iron out rust removal plan and system that improves the appearance of collectible mineral examples. Short soaking times, cleaning with a toothbrush or hi pressure cleaning gun, and repeatedly rinsing the specimen works for me. Unless I have a $1000+ specimen, I don't believe in using distilled water. Rinsing in and soaking in fresh tap water in the vast majority of the USA works just fine for most collectible mineral specimens. CHEERS......BOB

16th Aug 2016 14:40 UTCHarold Moritz 🌟 Expert

"Unless I have a $1000+ specimen, I don't believe in using distilled water. "

And you shouldn't use it, especially for the $1000+ specimens, because of its low pH...tap water is very close to neutral, unless you have bad well water, which I do, in which case you need treatment for it for more important reasons...like home brewing. :)-D

I suggested it in this case to see if perhaps the tap water was an issue, but I cant see there being (or sure hope there aint!) elements in it at high enough concentration to cause such a problem...

16th Aug 2016 15:11 UTCEric Briggs

A short soak in oxalic acid has gotten rid of the green stains for me in the past, and it just works better and faster in my opinion. I don't even bother with iron out anymore, unless the specimen calls for it.

16th Aug 2016 15:30 UTCHarold Moritz 🌟 Expert

Hi Eric. Good to know oxalic acid will remove the green. HCl would probably do it also.

Very true about its efficacy, but oxalic acid is toxic and is not safe to pour down drains or especially into septic systems. SIO is much safer to use and to dispose of, so I recommend using it only where one is prepared to deal with those issues. Also more difficult to purchase oxalic acid, I can easily get SIO at my local hardware store. Oxalic acid can also create an insoluble hard yellow precipitate on specimens if not mixed correctly, so be very careful. Probably not friendly to calcite or other carbonates either.

16th Aug 2016 17:45 UTCAlfredo Petrov Manager

Green iron oxides are somewhat unstable so, if you leave the greened specimen outdoors for a while it will turn back into a yellow-brown limonite stain and you can put it back in fresh iron-out and continue the cleaning.

16th Aug 2016 18:16 UTCEric Briggs

Hello Harold,

It is true that oxalic acid is more toxic and should be handled with great care! It has very corrosive effects on metal, clothing, people, etc.

It is also more difficult to find, especially what I consider to be the right kind. I prefer the powder, not the premixed solution. The powder allows me to fine tune my solution.

I haven't had any issues with the insoluble yellow precipitate, but I did read another thread in which someone said that citric acid in the mix would react with the iron that causes that, and keep it from coming out of solution. I haven't tried it though.

The main thing is that I always use it hot (about 120 degrees) and never let it cool down with specimens in it (this goes for iron out as well). When they're ready to come out, I immediately rinse them and move them to clean hot water (generally as long as it was in the acid) replacing the water a few times to make sure there's no residual acid left.

Using hot oxalic acid has greatly shortened the time to remove the stains as compared to even hot iron out, in my experience, but this is by no means the right solution for every mineral. I always test first!

16th Aug 2016 19:07 UTCBob Harman

ERIC, Powdered oxalic acid is marketed as WOOD BLEACH and easy to find in most any hardware store in the US. CHEERS......BOB

16th Aug 2016 20:12 UTCHarold Moritz 🌟 Expert

Alfredo:

Now that you mention it, I did that once with a "greenie" and it went back to brown.

Eric:

Sounds like an excellent approach. I will stick with the SIO, given that I have a septic system only for disposal.

Bob:

Thanks for that tip, didnt know that!

17th Aug 2016 10:59 UTCJonathan Ertman

i use distilled water from start to finish change a lot ,add iron out after three days Jon

25th Aug 2016 09:56 UTCIan Nicastro

I had problems where I bought a fist sized smoky quartz from the California Blue mine that had been cleaned by another person and had green crusty stains all over it, which I assumed were from SIO or a similar chemical mix turning the Fe to 3+. I normally use phosphoric acid in a sealed bucket in the warm sun for removing traditional colored rust... However putting the green stained quartz in the phosphoric was NOT a good idea... the green started turning to typical brown colors In some spots, especially in the fractures. The specimen was better off with the green crust. I'm assuming I would need strong hydrochloric at this point. The crystal has a lot of very complex faces and rough surfaces so it's not an easy job to manually remove the material, a water gun was useless. It was interesting to hear that people have success putting in oxalic to remove the green.

25th Aug 2016 15:57 UTCVolker Betz 🌟 Expert

Hi,

the green hue is caused due to reduction of Fe (III) to Fe (II), the colour of Fe²⁺ is green. This can be dissolved with muratic acid, alternatively with citric acid ,ascobic acid, formic acid, acetic acid (vinegar) or oxalic acid . The last only if the mineral is free of Ca, otherwise a (white) layer of unsoluble Ca-oxalate ist formed.

I some cases hydogenperoxide is a tool to remove the green layer, it als oxidizes the Fe(II) to Fe (III) again.

Volker

25th Aug 2016 19:29 UTCAdam Berluti

As Harold said, it usually happens to me with the feldspars from various pegmatites, though not always. It freaked me out the first time that happened but it wasn't a problem. Try soaking it in water for at least twice as long as it was in the SIO, and maybe even switch the fresh water a couple times and it should be fine. If you don't soak in water afterwards even without the green stain, you will end up with a white powdery dusting.

Volker:

Thanks for the explanation of the green staining. It always bothered me why it formed. That makes sense.

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