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Help Cleaning Brazilian Emeralds

Posted by Terry  
Terry November 09, 2004 02:35AM
Hey Everyone,
I purchased some mine rough emeralds on Ebay so I could say, I have emeralds in my collection, my question is , what would be the best way to remove some or all of the surrounding rock matrix, for the most part it appears to be mica, one large piece seems to have a white rock under the dark mica layer, along with some nice emerald crystals.
Thank you
Jolyon November 09, 2004 07:42PM
The white rock is almost certainly quartz (as it's Brazillian, for the Colombian emeralds this would be calcite).

THe best way to remove this is by hand using a steel dental pick and scraping away carefully at the mica to reveal the crystals.

Gunnar Färber November 10, 2004 10:37AM

It give a way to do it. But before I tell it you, I have to know how profesional you in the handling of dangerous chemicals. It give also a very good mechanical way, but for it you need a very good equipment.

Best Regards

Terry November 10, 2004 07:31PM
I know enough about chemicals to say I know how to handle them. Depending on which chemicals I may not be able to get them without a permit where I live.
LindaA December 10, 2006 10:09PM
I also have rough emeralds. Most of the ones I have are in a iron matrix. Very dirty and I have use muractic and also battery acid, not together. This works pretty good, but I'm also looking for a better way to clean them before i try faceting them. Any suggestions out there.
Barry Flannery December 10, 2006 10:44PM

Do not suggest that chemical as unless he is a phD Chemist or has access to a laboratory he shouldn't be using it!

Anonymous User January 04, 2007 09:18PM
Hi all!

First of all,why to remove the matrix?In general it is thought the best specimens are either floaters or have a nice matrix so the display beautifuly!Take my advice and do not remove the matrix.I would suggest a trim work on the specimen so that the emeralds are better seen.This has to be done very carefully,with metallic tools,always removing(braking) a small piece of the matrix and trying not to harm(brake)the emeralds.There is always the option trading these emeralds for emerald crystals and do not destroy the specimens by removing the matrix.

However,if you insist on removing the matrix,you have to do the following:

1-Carry your emeralds to a specialist for diagnosis(identification) of the matrix mineral(s).

2-Then goes the chemical removement.This is a very dangerous process,so do not be mad to the guys who do not want to tell you about it.I hope i can convince you by saying that a tiny drop of this acid fell close to my eye!1 cm saved me of losing my eye-I was very lucky!!!So,if you are not a specialist,or very familiar to the chemicals,do not risk your life,it's more important than emeralds.Go to you local museum(where you may have a specialist make the diagnosis)and ask a specialist do the job for you.

Anyway,I can tell you which chemicals to use and how,but think about it very seriously before you ask me to.Otherwise,I'd be glad to help.

Anonymous User January 05, 2007 07:10AM
I have some of these emeralds too, and would be very interested in the chemical means to clean them, as dental pick cleaning has not been entirely satisfactory. They are lapidary rough, and the attached bits of matrix are not enough to make the crystals an interesting display.

I understand the concern that keeps the formula off a public board like this. While he does not have a PhD, my brother is a certified haz-chemical handler (he works for a semiconductor factory), and has agreed to perform the cleaning for me, even if it is HF or HBF, in the proper manner. How can I contact you for the cleaning formula?


Gerard Martayan January 05, 2007 10:33AM
I own a few Colombian specimens with the usual black/gray shales and/or calcite matrix.
Emerald crystals are partly embedded in the shale and/or in the calcite and I'm tempted
to trim some crystals so they can be better seen.
Are metallic tools the only recommended way to go for a trimming work on "Colombian" matrix?
Anonymous User January 07, 2007 02:10PM
Hi all!

Yes,no problem,fell free to contact me,I just do not guarantee success,I hasn't try it myself on my emerald.Note that if we're talking about quartz,it's dissolvable nearly to any acid instead of one.But,since beryl(emerald) is totally non-dissolvable in any acids,you can give it a try!

Please let met know your email,so I can let you know.

Best regards,
Gerard Martayan January 07, 2007 05:32PM
Thanks Kostas.
You can contact me at

Best regards

Anonymous User January 08, 2007 11:00PM

you can contact me at:

tcregOOl (the last three digits are zero zero one) circle-A
earthlink / net

Thank you,

Martin Hanckel July 01, 2007 01:13PM
I am an industrial chemist and used to handling many acids, such as Hydrofluoric,hydrochloric,sulphuric,nitric, phosphoric and other mixtures.
What acid or acid mixture will clean the matrix from Brazilian emeralds.
Thanks Martin
yahya kader September 16, 2007 04:35AM
hey i would like to no the name of the chemical u were referring to clean rough emeralds, is it HCL hydrocloric acid??
Elba April 04, 2008 02:19AM
I have no access to acids, just vinegar. Any tips would be great. It is the first time I am doing this. I am a novice.

Tim Jokela Jr April 04, 2008 05:12PM
I'd suggest that Brazilian mine run emerald isn't worth risking life and limb over. You can make an excellent probe tool by sharpening the butt-end of a broken drill bit on a grinding wheel and mounting it with epoxy in a wooden dowel handle.

When that grows dull, graduate to a Foredom or Dremel tool for speedy matrix removal. Protect your eyes and your lungs!

A fair number of people tumble the stuff, but it takes some time.

Using vicious acids like HF on ten buck a pound stuff is madness. One drop on your skin and it eats right down to bone... and you can't wash it off... sound fun?

Peter Haas April 05, 2008 08:47PM
"I am an industrial chemist and used to handling many acids, such as Hydrofluoric,hydrochloric,sulphuric,nitric, phosphoric and other mixtures.
What acid or acid mixture will clean the matrix from Brazilian emeralds."

If you are, it should be easy as pie for you to find that out.
Joe Moore April 22, 2008 03:08AM
LindaA Wrote:
> I also have rough emeralds. Most of the ones I
> have are in a iron matrix. Very dirty and I have
> use muractic and also battery acid, not together.
> This works pretty good, but I'm also looking for a
> better way to clean them before i try faceting
> them. Any suggestions out there.

I soak mine in oxalic acid; it takes awhile, usually about a monyh of soaking but works great and is gentle. I agitate my jars every few days and watch the inprovement. I buy mine in crystal form so I can control the potency.
Jesse Fisher April 22, 2008 05:44AM
Most Brazilian emeralds I have seen are in a mica schist matrix. Micas are usually quite resistant to chemical attack, even HF. The only effective method to remove the matrix from around the crystal will be mechanical. Micas are also remarkably flexable, so air abrassives often do very little. What you are looking at is likely hours with a dental pick, or if you have some money to invest, getting a small compressor and a small pneumatic pick or scaler such as those made by Chicago Pneumatic.

Chemicals such as HCL and oxalic acid may be useful in removing iron stain or any carbonates that may be in the matrix, but will have no effect on the mica.
Claus Hedegaard May 12, 2008 09:12PM

Sorry to pick on you, but you present a common, misguided fear:

> I'd suggest that Brazilian mine run emerald isn't
> worth risking life and limb over. You can make an
> excellent probe tool by sharpening the butt-end

Chemicals as such are not dangerous and you do not 'risk life and limb' by responsible use of chemicals any more than you do by mechanical tools, possibly even less.
I started using chemicals when I turned 10 and now I have little letters after my name. I never had any problems with chemicals but have seriously injured myself using hammer, chissel, hydraulic splitter and other mechanic tools. Yes, I had proper instruction & guidance before using either.

Chemicals are the right solution to many problems - cleaning minerals & others. Ask people and have somebody show you before you start and do not experiment on your best piece. Evidently use gloves, ventilation, proper vessels, etc.

Honestly, who in his/her right mind would ever enter a mine, given all the potential dangers? Don't be stupid and be informed before you start, but do not let fearmongering prevent proper use.


Claus Hedegaard
Google me to find me!
John Hayes February 06, 2009 04:01PM
I have a minor in chemistry, you can use acids safely if you have correct safety equipment and procedures. You can research for free at Hydrofluoric acid is probably not a good idea for beryls or other silicon based minerals. It could ruin your stones, and for beryls or other gemstones that contain highly toxic elements such as berylium in their crystal matrix or chemicals that will react with the acids, it is dangerous.. FYI wear a respirator when grinding emeralds with cutting equipment of any type ( dremel, cab cutter, etc), wash hands and face carefully immediately after such work. HF is a pain to handle, anyway, since it etches glass and the fumes are highly dangerous, true for any concentrated acid, even hydrochloric. Oxalic acid is toxic, but should dissolve or at least soften a mica-schist matrix if kept over 160 degrees F (but well under 221 F ) for day or two, several weeks at room temperature with replenishment of acid and water as material breaks up--- some emeralds are loaded with gas and water inclusions, so don't bring them anywhere near the boiling point of water at your altitude--they may shatter. If you are uncertain, pick out a few pieces of "jardin" with obviously formed colorless or dull greenish crystals, and experiment with them. They are probably only good for the garden, anyway, as the name hints, so if they become shattered, no great loss. NEVER mix acids, this can be fatal, never pour water over concentrated acid (common sense test--if the acid produces fumes when container is opened,it is concentrated)--this can be a horrible mishap--I have seen both accidents in the lab.
Rock Currier March 05, 2009 08:36AM
You will need to post a picture of your EBay emeralds. With a picture to work from and to ask questions about you will probably get a much more focused response to your question and a much better chance of improving the value of your specimens.

Rock Currier
Crystals not pistols.
PTF August 12, 2009 04:29AM
Mine are not Brazilian, they come from the US and I wanted to do the same thing. A gemologist told me to use 50% muriatic acid as a soak. I read to use coca cola and have been doing that... down 2 bottles of coke but the emeralds are coming up nicely and there is no danger.

The gemologist also said I could tumble them with sand and that would wear away the shist. I don't have a tumbler so that isn't an option right now.

How did yours turn out?

Scott Sadlocha August 12, 2009 01:29PM
I have some of these as well, and have been looking for a way to clean them up a bit, though I am a bit wary of using chemicals as I don't have any formal training in their use. However, I am extremely safety minded in all that I do, so I would be willing to use somewhat common chemicals if instructed well. I do a lot around my home with tools, and have never had an accident, but I believe this is because I go overboard with regard to safety. I have some rotary tools, as well as a compressor and quite a few other tools, so I may try mechanical means to clean the samples.

The samples I have are most likely Brazilian, and look to be in a mica schist matrix as mentioned by someone else. I am at work now, but I will try to post a picture later today when I am at home. I know they are really not worth much, and just want to clean some of the matrix off to get a better idea of the crystals/structure, as well as practice my trimming skills.

One other thing I have noticed with them, is the fact that they have a strong odor of oil or petroleum. I figure that this is the result of their extraction method, in that some type of tool was used as well as a lubricant. I am just curious if there is some easy way to clear the smell from them. Thanks-
David Von Bargen August 12, 2009 02:33PM
One other thing I have noticed with them, is the fact that they have a strong odor of oil or petroleum. I figure that this is the result of their extraction method, in that some type of tool was used as well as a lubricant. I am just curious if there is some easy way to clear the smell from them.

Nope, oil is sometimes used as a "filler" to make the stones look better.
Tim Jokela Jr September 14, 2009 04:08AM
Hell, I love chemicals, and even have a T-shirt that says so, but I stand by my opinion that somebody buying low grade emeralds from eBay is perhaps not in the position to be using hydrofluoric acid.

Though of course I may be mistaken, and they have a nice little lab in the backyard, complete with fume hood, quality safety gear, and waste disposal procedures. Backed up by some education and hopefully that ever so rare ingredient these days, common sense.

I don't want to get into a huge discussion about relative risks, but some would say there's little to no risk in the average mine. Call me a paranoid fearmonger, but look at it this way: we live in a world where people severely burn themselves with cups of coffee, then sue for millions.

So no, let's not encourage folks to go out and play with HF to make semi-attractive green rocks slightly more attractive.

(No disrespect to Brazilian emeralds, I just bought a couple, but they certainly don't compare to Colombian, for which I would gladly perform my chainsaw-juggling act, blindfolded, on a tight-rope, over a pool of acid, while drinking extremely hot coffee.)

PT November 10, 2009 10:20PM
Hi, Would you share how strong an oxalic acid solution you use? I have NC emeralds I would like to clean up.

Rock Currier November 11, 2009 04:43AM
Are you trying to clean the "iron stains" off of your emeralds? If so, consider using iron out rather than oxalic acid. You can treat your emeralds like quartz crystals in so far as chemical cleaning is concerned. See the article on cleaning Quartz.

Rock Currier
Crystals not pistols.
Just a beginner March 09, 2010 11:03PM
I bought the emeralds on E-Bay and was wondering how to clean them, have them faceted, polished.,etc...Does Coca-Cola really work? Because if it does that would be the best way for me. Not very expensive, safe, no guess work, etc..
Adam Kelly March 10, 2010 11:46PM
I think you will need more than coca-cola to facet emerald.
First off, are they facet grade?
If not, are thet cab grade?
How many do you have?
Where are you located?
Could you post a picture of the emeralds?
Julia May 03, 2010 08:38PM
I have columbian emeralds too and if you arnt in a terrible rush the matrix can be disolved in soda water, so you can buy bulk soda water from your local costco, sams club and walmart the soda water should be pored into a plastic or styrofoam cup and then add the emerald ore. it will fizz and bubble moderately and after and hour the water should turn kinda merky and the fizzing from the rocks will slow at this point u can dump the water and replace it with new soda water the rate of replacing the soda water may vary depending on how much emeralds you put in and the amount of matrix on it just remember this may take weeks to complete removal however it truly is completely safe. and only requires time and soda water which like all carbonated beverages contains carbonic acid.
doug elenbaas December 12, 2012 07:36PM
would you tell me what acid you know of to remove the matrics from the emeralds and what process you use or know of. thanks
Rock Currier December 12, 2012 10:34PM
What kind of matrix is on your emerald? Can you post a picture of it?

Rock Currier
Crystals not pistols.
Rajendrasinh October 17, 2015 10:42AM
how to clear this emerald rough which chemical using?
Wayne Corwin October 17, 2015 02:07PM

Clear them of what?
Reiner Mielke October 17, 2015 05:26PM
He may be refering to the brown rust? If that is what it is then I would recommend ironout or equivalent, or oxalic acid.
Meyeusername April 20, 2016 03:02PM
I've gotten rough emeralds a few times and the safest way that I learned from the guy I was getting them from is actually just throwing them in a rock polisher. Emeralds are harder then the matrix they are in so just a tumble or two and the matrix gets broken away leaving the emeralds pretty untouched. I know that some of the weaker specimens can break but on the whole you are left with nice chunks of matrix free emerald. (I tend to just cab them)
Jean Coulombe January 11, 2017 03:05PM
Basic cleaning of the rough can be done with a scratch awl that has a steel tip with a high hardness rating (above RC-50 is good). Be careful, as the awl might slide across the material and get you in the holding hand - as I've learned many times. The tip may be used to pry at crack and to remove lighter material.

Rock polisher: buy a good one. The ones you get at a walmart-type store are usually a total waste of money. Look on ebay to get an idea of what a proper one looks like (price range: $100 to $500, varies according to volume that can be treated at once and motor strength). IMPORTANT: a rock tumbler turns slowly and needs time to do a good job; the cheap ones turn too quickly.

Cleaning emeralds with acids:
Don't use ANYTHING with fluorite - hydrofluoric acid reacts with beryl and will probably damage your stone way beyond repairable.
Muriatic acid (the stuff used to clean basement cement floors) is a good agent. But, like any acid, wear proper equipment. Read the instructions, understand them, follow them, and take ALL the necessary precautions (like working in a well ventilated area, wearing goggles, and adding water to acid - and not the other way around). Muriatic acid emits fumes: if there is any metal around and you are working in an enclosed environment, the metal will be corroded over a somewhat short period of time. Iron and steel will rust, and aluminium will become crumbly. I ruined a $50 router bit finding that fact out.
Sulfuric acid is supposed to work better, but I need a permit to acquire some, so I haven't had a chance to check it out.

Make sure you neutralize the acid after you are done (adding water only weakens it). A base will do (baking soda works fine).

If you are uncomfortable using acids, don't use them. Their mishandling can lead to extremely serious problems (including breathing and other health issues).

Rotary tools (Dremel, Foredom): get one with a strong motor. Foredom uses 1/3 HP motors, which can be used all day long. Dremel uses mostly 1/6 HP motors, which are designed for short light use. If you use a light motor for hours on end, you will quickly burn it.
For emerald cleaning, I use the green (corundum) rotary heads (not the polishing ones, which contain rubber and wear away within seconds). They take away the black matrix rather easily, but, because their hardness is not much higher than that of emerald, they slide across the emerald a lot without damaging it (when putting medium to light pressure on the tool). You may use diamond heads, but they chew right through emerald; not a good thing - I've ruined a bit of nice rough learning that.
Blue ceramic heads don't work at all on emerald: you might as well take your money and flush it - you'll save yourself a trip to the store and some aggravation.

If you decide to use diamond heads, go sintered. The plating on plated heads wears out quickly and tends to peel.

For best results with a rotary tool, try grinding away with the material and the head under water (1/2 inch below the surface is plenty), in order to dissipate the heat and contain the dust. You will get water spray once in a while. Please note that water might stay on the head after you are done, or even get into the rotary tool shaft while in use and rust away the cable inside. So, make sure to dry everything up after use, and to do the proper maintenance a bit more often than regularly.

Using a rotary tools requires patience (like anything else in the rock, gem and minerals field). As soon as you start using excessive force, you've got problems coming up.

Hope all of this is of some use.
Don Saathoff January 11, 2017 03:40PM
Jean, it is A to W, acid to water!
D. Peck January 11, 2017 04:08PM
Hi Jean, As Don pointed out . . . you add the acid to water. This allows greater dissipation of heat and avoids spattering due to small steam explosions. (suggest you edit your post for those who read it, but don't read Don Saathoff's or mine.)
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