FMF - Friends of Minerals Forum, discussion and message board

[daviddillman]

I recently bought several wavellite specimens that have significant iron stains on the matrix and the wavellite crystals. What chemicals can remove the iron stains but not damage the wavellite? There are a few places on some of the specimens that appear to be wavellite "balls" covered with a light crust protruding from the matrix. Any ideas on how to safely remove the crust?


I bought the specimens at an estate sale so I don't have precise locality information. However I have good reason to believe the former owners spent time vacationing in Arkansas.

[GneissWare]

Try super-iron-out. It comes as a powder. Mix with water and soak for 30 minutes at a time until stains are gone. Test on one piece first, although most minerals seem stable in it.

Also post some before and after photos.

[daviddillman]

Thanks!

[Peter Megaw]

Once again thumping the tub for Sinkankis's "Gemstone and Mineral Databook" (long out of print but this has a great section on cleaning minerals! Find a copy somewhere)

Sinkankis notes that wavellite is soluble in all acids, especially sulfuric and that any acid rapidly causes loss of luster. Also avoid strong detergents and ammonia. Ultrasonic works to dislodge clays.

This may contra-indicate Iron Out but trying it on an inconspicuous area is worth a go...and a good general practice before cleaning anything

More importantly it is very probable that the iron-oxides were deposited from an acidic solution and that the luster was naturally damaged by the staining process. In this case there is little to lose by trying Iron Out since iron-free without luster is still better than iron-stained without luster.

Iron out works a lot better and faster at elevated temperatures...I often use it outdoors in a crock pot (once I know it won't harm the crystals)...it will do whatever it is going to do in 15-20 minutes, so you may need repeated treatment in fresh solution (adding fresh powder to a "spent" solution does not seem to work well). For more sensitive minerals I simply put them in a large glass jug filled with iron out solution and put it in the sun...like making sun tea...but don't mix them up!

[bob kerr]

one other iron stain challenge: the attached photo is of a shangbao fluorite and calcite. note that two of the xls are nice and the largest xl is iron stained. how would you suggest getting the iron off the fluorite but not damage the calcite?

I've considered coating the calcite with wax or possibly dripping iron out on the fluorite and hopefully minimize calcite damage.

any other thoughts?

I also hope that the iron stain is on the surface and not internal to the fluorite - I can't easily tell - probably need a more powerful scope than mine.

thanks,
bob

[GneissWare]

Super iron out (SIO) has a pH of 5.5 - 6. It can be buffered to make it closer to pH of 7, but I can't remember right now what to use. I have not used it to clean Calcite, but my understanding is that it can be used in many cases -- although it is always best to test on scrap pieces to make sure. There are a few minerals that it destroys, so always test.

Rock Currier has a section on SIO at https://www.mindat.org/article.php/403/Cleaning+Quartz which describes the chemistry.

There is also a discussion thread at https://www.mindat.org/mesg-19-28652.html

It is best to clean in a covered container -- I use disposable "tupperware" which provides an air-tight seal. I have never heated it, and keep it out of the sun as I remember reading that it photodissociates. I have generally had good results in 30 minutes to an hour, and like most chemical cleaning agents, I check to see if it is clean enough as I don't like over cleaning.

[Peter Megaw]

This looks like a prime candidate for Iron Out and either the Sun Tea approach or a crock pot. The principal concern here is thermal shock on the fluorite...not necessarily high temperatures but rapid temperature change could cause it to cleave. Shangbao is a skarn deposit so this fluorite formed at high termperature...well above boiling water...so if it was mine I'd go crock pot. I'd put it in plain water, bring the thing to a simmer, then add iron Out. Cover and simmer for an hour or so, then turn off the pot and let the thing cool down overnight. You might have to do several repeats if the oxides are deep into the cracks.

To be cautious you could try the sun tea approach. A mayonnaise jar would work. Put in specimen, fill with water, add Iron Out and set it in the sun for several hours. Then put it in the shade to allow it to cool down slowly.

In no event put warm or hot fluorite into cool water!

The calcite should not suffer at all from the IO treatment but you can mask it with wax if you want. Danger will come when using hot water to remove the wax

[Jordi Fabre]

I would suggest to try first a small portion of that Calcite in Iron Out. If the Calcite becomes dull, then don't use Iron Out. As Peter point out the wax could be complicate to remove by the Fluorite.

[bob kerr]

thanks for the tips - i'll give it a try and post results. I thought that iron out was a pretty strong sulfuric acid and would "fizz" the calcite.

I've only seen iron out as a liquid? would home depot/lowes carry the powder or would the liquid be strong enough?

thanks again,
bob

[GneissWare]

Iron Out is not the same as super iron out (SIO). SIO is sodium dithionite.

[bob kerr]

so, super iron out is a powder and when you add water it becomes iron out??

sorry but i'm confused.

bob

[GneissWare]

[Barry Vincent]

Oxalic Acid hasn't been mentioned here yet. I use it now and again and have had no problems as yet.

[bob kerr]

[bob kerr]

in the previous posts, some excellent input was provided by gneissware and pete megaw concerning removing iron stains. I have two specimens of fluorite and calcite from shanbao in china that I bought at a discount due to the fact that the had iron stains on them. I was concerned about cleaning with any acid as it would probably damage the calcite so "super iron out" was suggested.

I bought a container of super iron out powder at lowes (it was actually cheaper there than on ebay) and mixed up a batch and soaked the two specimens twice for over an hour each time at room temperature. results are shown below.

to summarize - the iron out works! - when it's possible for it to work. what I mean by that is that the one specimen is not coated with iron stains, the iron is internal to the specimen itself and cannot be simply removed, however that one specimen that had surface iron cleaned up nicely - both the fluorite and the calcite.

that's for all the help - I need to get sinkankas's book.
bob