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Cleaning Fluorite

Posted by MG  
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MG September 11, 2004 09:50PM
I have a nice specimen of fluorite that has a layer of calcium carbonate, or hardened mud on it and I'd like to get it cleaned without damaging the specimen. Any help? I was told a high powered water blaster might work.
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Lloyd L September 11, 2004 10:47PM
If it's mud, a high pressure water gun (sprayer or washer) should work.
If it's calcite, you'll need some sort of acid. Any acid will work, but you have to consider what it might do to the rest of the specimen and the risks involved to your well-being. Although organic acids such as acetic (vinegar) or citric should work eventually, inorganic acids are faster but present a greater health hazard. Commonest seems to be hydrochloric but many people favour phosphoric as this also has the beneficial side-effect of working on iron-stains too. Phosphoric acid is available in domestic rust-removers such as 'Jenolite'.
If too strong an acid is used, it can etch the fluorite.
Whatever method you use, please, please be very careful and if you are not used to, and have no proper facilities for, handling acids, get some expert assistance. You should also wear eye-protection if you go down the high-pressure gun route.
Hope this helps and you end up with a worthwhile, gemmy fluorite.
Lloyd
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Peter Haas September 15, 2004 01:56AM
Be careful with mineral acids. They will convert fluorite to hydrofluoric acid to some extent, especially when used at higher concentrations. The fastest way is not the best way here. Phosphoric acid and sulfuric acid form calcium salts that are less soluble (more stable) than fluorite, so they will attack the fluorite to some extent even when they are dilute. This doesn't men that your fluorite will dissolve to any visible extent, but the brilliance of the surfaces might be gone after the treatment. Acetic acid is the best choice. Citric acid is a good complexant for calcium and, therefore, will attack the fluorite as well.

A water gun is also not a good advice: fluorite is sensible to temperature and mechanical shocks, so the crystals may crack. Mud is more efficiently removed by soaking in water for a couple of days. It often consists of clay minerals or of ill-defined metal oxides/hydroxides. They can adsorb considerable amounts of water, which makes them swell. However, adsorption is a physical process and hence, rather slow, so it will take some time.
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Lloyd L September 15, 2004 06:26PM
Thanks, Peter, I stand corrected.
More science and less brute-force is always a good policy!
Lloyd
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Gunnar Färber September 24, 2004 07:26AM
Hello,

if you have only Flourite there, you can clean it very well in HF. But please HF works good but is also very dangerous.

Best Regards

Gunnar
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PeterA September 24, 2004 12:00PM
Hi Gunnar,

HF is not only dangerous, it's lethal in quite small amounts - even as a spill on bare skin (clothes soked in acid might even be worse). If skin are exposed and not washed/threated with special lotion (I think it's some kind of Ca-ionic lotion that neutralize the HF) after a short time after the exposure, the damages might cause a painful and slowly death!

I was presented an article when I started work in the laboratory at university about a tragical death caused by HF (I think it was about 1dl, on less than 150 square-centimeters of skin!). I never worked alone on the lab with HF after that! So nobody should even consider using HF outside a well secured labb with easy way to get treatment and help if the accident should happen!!! Even very smal exposures on skin should be treated by doctor.

Regards
PeterA
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Danny September 24, 2004 12:24PM
The solution comes in a gel form and is calcium glauconate. It costs about £25 for a small 25g tube. But even this isn't really an "antidote". I'd advise against against using HF unless in quite controlled surroundings.. ie. a fume cupboard, full safety gear, a nearby shower for irrigation in case of a spill and obviously some calcium glauconate gel. In fact for the sake of a clean specimen id probably advise against using it fullstop. Nasty stuff!

Danny.
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Danny September 24, 2004 01:24PM
Sorry... Calcium Gluconate.. available from IPS healthcare as well i others i expect.
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Alfredo September 24, 2004 01:42PM
Available in the USA from www.attminerals.com
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Chris van Laer September 30, 2004 03:00PM
Fluorite is soluble in sulfuric acid (concentrated) and releases hydrofluoric acid in the process, so it's best to avoid this altogether. Fluorite is NOT soluble in hydrochloric (muriatic acid), especially in a dilute solution. Use only cold, do not heat, and allow to soak until all bubbling ceases. It is very important to properly neutralize all traces of any acid after even a short bath; this is easily (* and cheaply) accomplished by soaking for an extended period in a solution of common baking soda and water. This may liberate some carbon dioxide gas, so do not seal container, but allow gases to escape. Also, the dissolution of any iron compounds present will color the HCl yellow, which can soak in cracks and crevices or porous minerals and discolor the specimen yellow. This can be reversed if not allowed to completley dry out; if yellowing persists, allow longer neutralization in baking soda or soak in a solution of sudsy ammonia for as much as a week or two. If still yellow, soak in a bath of warm or hot oxalic acid; this will dissolve traces of iron chlorides, the follow with a soak in baking soda solution.
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Peter Haas September 30, 2004 03:22PM
Two comments:

Fluorite and HCl: Concentrated hydrochloric acid DOES attack fluorite to some extent (which is easily confirmed by the SiF4 test). The reaction is very slow and it is certainly not dissolved to any visible extent. Its brilliance may be lost, however, when it is exposed to the acid over a longer period of time.

Calcium gluconate and HF: An effective neutralization requires that the gluconate is applied immediately after the contact. This is a big problem, though, because HF is a rather weak acid. It does not etch the skin, it simply penetrates through it. There is big risk, that you don't notice anything, when you spill a small volume over your it. There are well documented examples of people who died within a few days after their hands or forearms had been contacted with a few milliliters of hydrofluoric acid for a short period of time.

Peter
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Alfredo October 01, 2004 12:16PM
Re Fluorite and HCl: Peter says "Concentrated hydrochloric acid DOES attack fluorite to some extent..."
This is true, but irrelevant to mineral cleaning, which is normally done with less than concentrated HCl. In fact, for many cleaning purposes, somewhat diluted HCl works better than conc. HCl.
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Peter Haas October 01, 2004 03:34PM
Alfredo,

That's right. But - do we know whether people who are posting here, have ever handled chemicals before ? Could we preclude that they simply don't know that there are less and more appropriate concntrations ? They'll likely play around with the chemicals they use: for instance, they will find out that increasing the concentration will speed up the process. People tend to become impatient when they have to wait every time for something to happen, so this apparent advantage will overweigh any precaution - especially, if you don't know much about chemistry: you'll never be going to think about side effects - unwanted competing processes that become dominant at higher concentrations, or a complete change of the chemical and toxicological properties, for instance - and even less about the hazards. I still remember a cleaning advice proclaiming the use hot concentrated sulphuric acid, given by someone in this forum a couple of months ago ... and that's another important point: heating speeds up some chemical reactions, while others are almost not affected. When minerals are cleaned, desorption and displacement processes at phase boundarys do often play an important role. These are physical processes and they respond to different parameters than chemical reactions do. The speed of action of an oxalic acid solution on iron stains, for instance, is higher when the solution is permanently stirred (of course, this is a bit problematical, when the specimens are in it) than when it is heated.

Actually, I have to be aware of all that when I recommend a particular chemical. I also have to be aware that there is always the risk of a hazard, when people are not used to handle chemicals. Therefore, I have to recommend working conditions that are safe enough for not seriously hurting a person and not imparting any permanent damage in case of an accident. I certainly can't guarantee for that when the chemicals are used at different concentrations or in different conditions and, therefore, I have to tell people what may go wrong if they don't exactly follow the advice. I will be fully responsible if something happens what I didn't point out. The most common reason for misuse of chemicals is ignorance. Of course, It's their own decision to use chemicals, but I can't expect them to act responsible, when they have not been informed about any imagineable risk.

Many people think of chemists as eiher acting irresponsible, or grossly exaggerating. The latter might be the reason why many collectors are more easy to convince, when they're told that there is a risk of a permanent damage to their specimens ... There is, honestly, rarely any exaggeration, though.

Peter
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Bob Reed October 01, 2004 06:29PM
Hi all,
45 years ago i worked in a steel works for a short time. My first job was to get a bucket of water and a carboy of Hydrofluoric Acid. I was then told to wash some skylight windows!! How times change. Needless to say the job was short lived.
Regards Bob
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lynna January 17, 2005 02:11PM
Hi all,
I have mixture of 1g of fluorite+calcite with me.

Anyone here could recommend me any reliable test so that I would be able to know how much of fluorite presence in my 1g of mixture of fluorite and calcite?

One of the possible solution is to clean the mixture with hydrocloric acid but anyone here could give me a clue about the recommended concentration of hydrocloric acid that I should use for this?

Thanks in advane

lynna
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David Von Bargen January 17, 2005 04:35PM
A 10% solution is used in testing for calcite and creates a rather vigorous evolution of carbon dioxide. I would suggest that you use a more dilute solution or you could "boil" the fluorite out of the test tube.

If you have an X-ray diffraction machine, you could also do a powder diffraction (with appropriate standards for peak height of pure materials) pattern to determine percentages.
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Sergej Martynov May 19, 2006 12:45PM
Hello, I would like to exchange experiences because of machine cleaning of CaF2 glass
the material does not stand which chemicals, which chemicals doesn't the material bear?
If somebody could help me, that would be super
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Zbynek Burival July 29, 2006 07:38AM
lynna: Just weight your specimen, then dissolve calcite in 5-10% HCl and then weight the fluorite. And here we go!
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Steven Austin August 18, 2006 06:17PM
Everyone has some great ideas and they are helpful, but I do not have the means to use the more "powerful cleaners". Also, I want to ensure my specimen doesn't get harmed. Any ideas of other cleaners to use? My specimens are from the Elmwood Mine (Carthage, Tn USA) and consists of Sphalerite, Calcite, Barite, Quartz and Fluorite and occasional Galena. Its the Fluorite I want to clean up, they have a dust or mud on them. Any help would be great!
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J. R. Hodel August 18, 2006 07:20PM
Hi Steven,

One thing you should be aware of is that using liquids with your specimen that vary in temperature from that of the specimen may cause the fluorite crystals to spontaneously cleave off a large piece due to temperature differentials. I used plain old soap and water on a very nice fluorite from Illinois, and because the water was a little different temperature than the fluorite, a corner of the most prominent cube pooped off with a snapping sound.

So use water (or any fluid) that has had the opportunity to reach the temperature of the specimen rather than hot water (or even ice water) on a specimen at room temperature.

I recommend just a simple room-temp soapy water solution and a soft brush - you could let the specimen soak for a while, as someone above recommended - but don't introduce sudden temperature changes or the whole thing could come apart.

JR in WV
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Steven Austin August 22, 2006 08:38PM
JR:
Thank you for the advice. I will try to develope my skills on a "less important" specimen. I'll let you know how things turn out! Appreciate the time and assistance.

Very Respectfully,

Steven
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Tori July 13, 2010 07:45PM
I have some fluorite crystal that I want to polish. Any ideas for cleaning it?
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Reiner Mielke July 13, 2010 08:29PM
Temperature can be a real problem since most acids are exothermic when diluted. Make sure the temperature of the fluorite and acid bath are the same. Same goes for the neutralizing solution.
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G. Matthews October 30, 2010 01:44AM
I have been using a 10 to 1 dillution of Muriatic acid to clean fluorite specimens, most of which are from China although some are from Kentucky. the specimens from China had a fine white coating on the crystals before I put them into the acid. the acid removed most of the coating from the crystals but it appears to have redeposited it on the matrix. Any suggestion as to what the coating is and how to remove it permanently from the specimens?
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Rock Currier October 31, 2010 02:33AM
Could we see a picture of a specimen that needs further attention? When you put them in the 10 to 1 dillution of Muriatic acid did the specimen bubble? How long did it take to "clean" she specimen?

Rock Currier
Crystals not pistols.
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Konstantinos Charalampidis November 25, 2010 07:40AM
Hello!


You could clean you specimen using a sand blaster with Calcium Carbonate as an abrasive.This won't hurt the fluorite.


Hydrofluoric should be treated with Calcium glauconate after the acid has come in contact with the skin.A doctor should measure the surface attacked and use the appropriate amount of the compound.The purpose is to provide Calcium to the organism,not neutralize the acid.

The problem is that particles penetrate all tissues,react with the calcium and the result is hypocalciaemia.Calcium has an important physiological role for the heart function,muscles contraction and nerve system.

It is possible that the patient feels no pain due to the burn,because the calcium needed to release neurotransmitters has reacted with the acid.

The gel form is used for local treatment,but a patient with a large area exposed should need an injection.

It's certainly not an acid that can be used by an amateur and not even by a professional ,if the goal isn't really important.

The cleaning of a specimen isn't important enough to put you life in danger.Health is not only a right,but an obligation!

There are professional trimmers who will clean with Hydrofluoric and the price is low compared to the danger.

Don't play doctor of chemist!You need to be alive to enjoy your specimens!

Good health to all of you!
-Kostas.
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Jonathan Woolley December 16, 2010 12:59AM
This seems like the right thread to post this question. I have an old specimen of fluorite, sphalerite, very minor pyrite, & quartz on a carbonate matrix from Illinois (Minerva #2 Mine) that I recently obtained. There is some slight iron staining on parts of the quartz that I'd like to try to remove.

If I use a Super Iron Out solution will this hurt the fluorites? I hesitate to use any acid because of the carbonate matrix, and I suspect that the piece may have been cleaned with acid in the past because the fluorite is somewhat dull already.

Best regards,
Jonathan
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Rock Currier December 16, 2010 04:29AM
Jonathan
Super Iron Out will not harm any of the minerals on your specimen.

Rock Currier
Crystals not pistols.
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Evelyn Anderson March 12, 2011 10:55PM
I recently bought a nice piece of fluorite crystal at a mine near Oatman, AZ. I scrubbed it with soap and water and some of it turned white. We have oxyrocks product and super iron out. Will either of those work to clean this piece up? It has a tiny pieces of black rock onsome of it. Evelyn Anderson
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Don Saathoff March 12, 2011 11:51PM
Evelyn, quite often fluorite is oiled or sprayed to enhance the color (making the surface of the piece more transparent so that internal color can be seen). I can't know if this is what has happened in your case but you might try a thin coat of mineral oil applied with a stiff toothbrush to see if the original appearance returns.....you can always wash it again to remove the new mineral oil.
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fayyaz nazeer January 19, 2012 08:12AM
hello!

i have tried fluorite crystals in HCL and HF but both types of acid effect the luster of fluorite very badly, so all user be very much careful in dealing with acids.
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Rock Hound in NJ September 30, 2012 09:49PM
I now have 2 pieces of flourite that I am trying to clean. The first one is pink and it has brown depsits on it. I tried white vinegar and oxalic acid. I also tried to physically remove the brown deposits with a small sharp knife but the brown is mostly still there and I believe I have white deposits too. should I try mineral oil?
The second piece is new and comes in the usual green/blue/purple colors. It had been stored in a rock pile outside exposed to the elements. When I purchased it my hands got all muddy so I though a simple bath would do. I soaked it in water overnight and used a toothbrush. The bowl of water now stays clean but the rock still looks like it is covered in mud. Do I go to the drug store and ask for muratic acid? I appreciate any help anyone can give me.
Lastly mineral oil is mentioned above. Does using vegetable oil cause a problem?
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Rock Currier October 01, 2012 11:49AM
Could we see a picture of what it is you are trying to clean?

Rock Currier
Crystals not pistols.
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David Zimmerman (2) October 01, 2012 11:16PM
Muriatic acid is best had at the hardware stores (big box ones) and sold as concrete cleaner or similar in 1 gallon jugs. I have had it pit some fluorites and yet others it works great on. Always try new techniques on inconspicuous locations or small chips.

Rock is right though, a picture would really help out.
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Edwina Lynn February 05, 2016 05:59AM
So jus a Luke wam bath in sea salt and water is not a good way to clean my fluorite?
Same with Labradorite?
Sea salt and water......?
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Alfredo Petrov February 05, 2016 06:23AM
Edwina, what does the sea salt do that water wouldn't do all by itself?
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Ranger Dave February 05, 2016 06:29AM
Sea salt? It's all sea salt.
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Susan July 08, 2016 04:31AM
I have been reading your advice on cleaning minerals very closely. Used a cleaning vinegar (6%) on a piece of petrified wood with, what I suspect, might be fluorite (since they stayed and did not leave on application of vinegar). I had read closely your discussion on acids and am of the mind that, unless you have the right equipment, most of the other acids are a bit scary. My progress is slow, but as the blue forest wood has slowly surfaced, I also don't have to worry about accidentally murdering myself. Strangely, I just had a teacher of rockhounding encouraging the use of muriatic acid. Your posts on the use of ammonia and vinegar have kept me from making what I believe might be grave, even deadly, errors. I almost went out and bought some but came back here instead and read all your wise words again. My chemistry teacher beat into us the careful use of acid, and base, especially HCl.I just wanted to thank you all, especially the guy reminding people that there are impatient people out there who do not use chemicals daily, or perhaps ever, and to whom "don't heat it," and "wear gloves, use ventilation, cover all skin, and wear goggles or maybe a face shield" are all foreign concepts. Again, thank you.
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Joyce August 04, 2016 02:41AM
I have worked with every chemical and poisonous gas known to man...but HF is by far the most dangerous! It will not burn your skin but it will absorbe into your skin and affect the nervous system, the one time I got it on me I had on three pairs of gloves, three aprons and a chemical mask and a full face mask..I washed with clear water first and then neutrilizor and still got it on me, just on the tip of my finger and within an hour I was in so much pain my boss took me to the hospital and they put needles up under my fingernails with out any medication to deaden it first because they had to know when the medication to kill the effects of the HF was working, they also had to cut my fingernail in half first before the needles...so if you don't know what you are doing stay away from HF!
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