SUPPORT US. If is important to you, click here to donate to our Fall 2019 fundraiser!
Log InRegister
Home PageAbout MindatThe Mindat ManualHistory of MindatCopyright StatusWho We AreContact UsAdvertise on Mindat
Donate to MindatCorporate SponsorshipSponsor a PageSponsored PagesMindat AdvertisersAdvertise on Mindat
Learning CenterWhat is a mineral?The most common minerals on earthInformation for EducatorsMindat ArticlesThe ElementsBooks & Magazines
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
Mining CompaniesStatisticsUsersMineral MuseumsMineral Shows & EventsThe Mindat DirectoryDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day GalleryMineral Photography

Techniques for CollectorsSomeone With Hydrochloric Acid

21st Jul 2019 17:22 BSTSean

Hey guys,

I'm looking for someone in Ottawa to help me etch a few (or some) of my minerals that I've recently found in California. Is there anyone in Ottawa who can help me etch them?

21st Jul 2019 17:40 BSTSteve Hardinger Expert

What are the minerals? How large are the specimens? How many? In the US you can purchase muriatic acid (hydrochloric acid) quite cheaply from hardware stores. Just yesterday I purchased two gallons for $USD 11.


Muriatic acid can be quite dangerous if mishandled. If you have any concerns about safety then you are correct to ask someone else with experience to handle the task. Quality specimens are worth the time and expense to ship to a professional for preparation. PM me if you want some suggestions.

21st Jul 2019 17:49 BSTBob Harman

C'mon SEAN, when in Toronto I was in a big box store and they had muriatic acid for cleaning lime on patios and pools. You surely should have the same in Ottawa.

Also you can easily get cleaning strength (6%) vinegar at any big box or hardware store. It is safer to use, works fine, but just a bit slower.

If your specimens are quality in type, send them off to a professional preparation lab. If ordinary in type, just carefully use the acid on your own.


21st Jul 2019 22:20 BSTSean

I know I can purchase them in Ottawa, but I've never used one before. Which is why I'm looking for someone to help me out.

Steve - For your question, I have Grossulars and some of them are covered with Calcites. For the size, some are small and a few of them are as big as my palms.

21st Jul 2019 23:21 BSTFrank K. Mazdab Manager

Hydrochloric acid is not particularly dangerous, unless you get a really good lungful of the fumes (so work in a fume hood or outdoors in a light breeze) or if you try to drink it (but why would anyone do that?). Safety goggles are probably always a good idea because splashes can be unexpected and the eyes are more sensitive (and obviously not replaceable) compared to skin. If you normally wear contact lenses, it's safer to switch over to eyeglasses during your chemistry work.

Still, you can spill the full strength acid on your skin and you'll suffer no ill effects (but be aware, if you have any pre-existing cuts, abrasions or bad cuticles, getting acid on those spots will sting like crazy!). Of course, you'll want to wash off any acid spilled on your hands promptly anyway, if for no other reason than you don't want to absentmindedly then go and rub your eyes or mouth.

If HCl were actually dangerous we'd have a national epidemic of dead and maimed pool boys... we do not. Of course, HCl should be treated with reasonable care, as should any chemical, but you needn't be paranoid about it... some drops on your hand and you'll wonder what the big deal was all about... one whiff of the fumes and you'll know to be more careful next time.

Have marble chips from the lawn & garden store or baking soda around to neutralize any spills (or work on a concrete surface). Excess acid, once fully neutralized, can be flushed down the drain (it's just salt water at that point).

22nd Jul 2019 00:38 BSTBob Harman


Frank has given you some good advice. As I have had extensive experience over 30 years, I will give my ideas of cleaning specimens with vinegar or hydrochloric acid.

First several generalities. I am assuming you are an adult, as I personally don't think youngsters under the age of about 15 should use hydrochloric acid unless under direct constant adult supervision. So, if you are younger than about 15 start your experience with vinegar.

Always be in an open, well ventilated space. Strongly consider using gloves and eye protection. When diluting acid, always pour the acid into water, never pour water into the acid. Always have a garden hose, bucket of water, or large sink readily available. Dilute the acid as necessary to do smaller areas.

When you are ready, do an evaluation of your specimens. What minerals do you have and might any of the minerals you want to save, in fact, be damaged by the acid cleaning process. In other words only acid etch when something you want will be saved and other stuff you don't want will be eliminated. What do you really want to accomplish? A good rule of thumb is that cleaning to materially improve a specimen is not that other words many low end examples will always be low end examples, no matter how we attempt to improve them. So to gain experience, first take your lowest end examples and experiment with them. Don't spend too much cleaning time or effort if the examples are of really lower end; after experience, concentrate your cleaning efforts on the highest end specimens.

Remember that less is better. Etch with acid as little as possible to gain whatever improvement you can gain. In other words just don't throw specimens into acid and leave them there; be time conscious. Many lower end specimens will just change color and fall apart with excessive acid cleaning.....not really being improved.

Rinse very well and, when using hydrochloric acid, then consider a baking soda bath followed by another good rinsing to counter the acid etching.

With some time and experience, at least some of your specimens might just really become improved.

As an addendum, I'll mention to set aside enough time for your project. You don't want to be rushed or get called away for other things in the middle of your cleaning. Make sure curious pets or small children are protected from the chemicals.

And, most importantly, if you really want help getting started with all this, LOOK TO JOIN A LOCAL CLUB where collectors with acid cleaning experience might assist you. CHEERS.....BOB

22nd Jul 2019 01:40 BSTAlfredo Petrov Manager

For removing calcite from garnets, hydrochloric acid is overkill. People use it because it is so readily available almost everywhere, and because they are impatient and want the calcite gone yesterday. But it has several disadvantages. You really should use white vinegar instead, which you can get at grocery stores. It takes longer, but what‘s the rush?

22nd Jul 2019 02:32 BSTSteve Hardinger Expert

Frank, ignoring appropriate safety concerns in an excellent way to become injured or even dead. Appropriate safety is about understanding what can happen, and preparing for it. Always assume the worst. Permanent lung damage from one whiff, for example, is quite possible. I'm not willing to swap a little laziness for permanent, life-altering injury.

And yes, I am a professional (retired) chemist with 35 plus years handling some very dangerous stuff.

22nd Jul 2019 04:42 BSTFrank K. Mazdab Manager

Steve, there's also the opposite problem, for example when you read the MSDS on sodium chloride or citric acid, is that people see the "hazards" written about generally harmless materials, and then wonder if similar hazards written for unfamiliar materials are real or just fear-mongering. Since it's unrealistic to assume most people don their hazmat suits and respirators when working with sodium chloride and similar materials (perhaps you do?), a better approach is to genuinely critically understand the actual dangers of the chemicals one uses rather than just relying on the "legally-required" notices apparently used only to absolve responsibility.

Is HCl harmless? Of course not. But nothing I wrote above is inaccurate... if you get HCl on unbroken skin, at most you'll experience a bit of itch if you have especially sensitive skin. And the odor is so penetrating that only having your nose over the bottle when you open it (foolish in any situation) would offer a whiff so severe to be dangerous to the average person... I have never heard of an instance where a casual waft (as is taught as the safe and proper way to identify chemical smells) has caused lung damage, permanant or otherwise, but I'd certainly be open to see your references on such instances. In any case, even that minimal hazard can be further minimized in a well ventilated area.

HCl is one of the most commonly used industrial and home chemicals (the latter especially in states with lots of pools)... I can't recall any news articles about deaths or injures with reasonable use, and with all the idiots out there who undoubtedly aren't especially safety-minded, you'd think in Florida, Texas, California, and Arizona especially there'd be several such stories every summer. While you may disagree, what I wrote previously is sufficiently careful use for a relatively low hazard acid (that in more diluted form is our stomach acid).

I too am a chemist by education, and have also worked with some nasty materials (notably HF and HClO4) that obviously require much different and more rigorous safety handling precautions (indeed, those two example materials are chemicals no amateur should work with).

22nd Jul 2019 08:35 BSTKevin Hean

Hi Frank

I am with Steve on this one, One whiff of HCL WILL destroy some of your smell receptors, permanently finished klaar and kaput for good,

Each time you catch a whiff some more are destroyed and you will slowly loose you sense of smell, also not a good idea to clean fluorite with HCL

22nd Jul 2019 10:08 BSTFranz Bernhard Expert

It strongly depends on the concentration of HCl (and all other chemicals diluted with water).

HCl fresh from the bottle is about 30%. It produces really, really nasty fumes. I would not do much with it, except directly poor it in water from the original bottle to dilute it.

When you have a concentration <10 %, no more HCl fumes come off. However, during dissolving carbonates, CO2 is produced and the diluted acid is finely dispersed with the emerging bubbles, forming fine mist / areosol. I do not recommend to breath it.

Important: Eye protection is always necessary, irrespective how diluted it is.

I would not use gloves, if the HCl is diluted <10% . I have always the fear, some acid goes unnoticed under defect gloves and does its work on my skin unnoticed. You have a better control over spills with bare hands. Just wash it of, if you spill yourself with drop or two. And if you already have microinjuries on your hands and fingers, you will notice the spill immediately, as already stated.

This does not hold true or HF etc. Gloves you can rely on are must in this case, irrespective, how diluted it is.

Franz Bernhard

22nd Jul 2019 11:30 BSTFrank K. Mazdab Manager

I suppose everyone has a different tolerance for the risks of perceived hazards. I started working with HCl when I was a teenager responsible for keeping the backyard pool clean and sparkling, and then on through the present in my periodic use of it as a chemist, geologist and mineral hobbyist. Certainly during my youth, the number of times I got an accidental whiff of it or splashed a bit it on my hands (those heavy glass 2 Liter jugs were not very pour-friendly when aimed at a 50 mL beaker) must have been innumerable; despite those experiences, however, I seem none the worse for wear. None of my friends at the time, also typically responsible for the upkeep of their families' pools, also seem none the worse for wear (at least among the couple I still keep in touch with). In retrospect, though, looking back at my youth in south Florida, what actually really amazes me is that in all the times my friends and I opted to go swimming in the murky weed-choked lake behind our houses rather than in our crystal clear pools, that we never had an encounter with an alligator, any venomous snakes, a snapping turtle, or those brain-eating amoebae. Now, older and wiser, I wouldn't be so quick to splash around in those lakes. But the routine handling of muriatic acid? no worries, then or now.

22nd Jul 2019 16:59 BSTMatt Courville

Frank and Steve are both right depending on the experience of the user. I've used this acid daily in a laboratory for a decade, and it was no threat because I had proper tools and experience to deal with it.

Safety is often subjective (not that it's the right approach) where if I were to ask 10 people I work with if HCl is safe to use for etching calcite, there would be a 50/50 split of opinion. Read the 'Safety Data Sheets' when you use something new (all over the internet) and have the proper equipment ready. If you are nervous, don't bother and simply avoid using HCl to opt for vinegar instead - even heated in an old crock-pot in a well ventilated large yard will work. Changes of the vinegar will be needed once the reation is exhausted.

22nd Jul 2019 17:28 BSTAlfredo Petrov Manager

I don‘t even need to go to a hardware store, as my local supermarket sells 23% HCl along with their other cleaning supplies, and they recommend the HCl to anyone looking for something to clean off the crusts left by hard water in toilets, bathtubs, etc. No age limits... teenagers can buy it for science experiments. So obviously it is not considered a very dangerous chemical, at least not in this less-than-concentrated form.

When I lived in Bolivia, HCl was prohibited, not because it was dangerous but rather because people used it for purifying cocaine, so for mineral cleaning we collectors had to use nitric acid instead. In fact Rock Currier used to recommend nitric acid rather than hydrochloric for cleaning carbonates off of silicates because he said nitric acid had a lower propensity to dull the luster of silicates. But in general I still prefer vinegar (5% acetic acid)... very weak, and slow, but I have patience. As Matt said, you‘ll probably need to switch to fresh vinegar a few times, but it‘s cheap. Incidentally, vinegar even works on tougher carbonates like dolomite - Just be patient.

22nd Jul 2019 18:21 BSTDonald B Peck Expert

I, too, am a trained chemist. I agree with Steve. It is best to know what can happen and be prepared for it. I also agree that HCl is one of the least hazardous mineral acids. Never-the-less, one does not want to get splashed, on the skin or especially in the eyes with anything approaching the concentrated acid. We shouldn't be afraid of the stuff, but we should respect it. ALWAYS, wear eye protection (Frank's tip on not wearing contact lenses should be mandatory.) Splashes on clothing: get out of the clothing and rinse the skin with water (the cotton clothing is going to develop holes). And with the concentrated HCl, dilute it or work with out of doors . . .and I agree, keep it downwind from yourself (or anyone else).

And last time I looked, Concentrated HCl was 38 or 39% hydrogen chloride.

22nd Jul 2019 23:31 BSTSteve Hardinger Expert

Anyone who thinks appropriate safety precautions are foolish deserve their fate. I know of at least six students -- undergraduate or graduate -- who were injured in (in one case) killed because they took safety too lightly.

Proper safety -- a safety culture -- is about anticipating problems and acting to prevent them. Reactive 'safety' -- what most people practice -- is about 'goddamn that hurt my eye is gone along with three fingers should have worn safety glasses".

Jolyon, I'd like to propose that this topic be closed so no one can say 'I read about [this stupidity] on Mindat and they are smart people but I was hurt so I will sue Mindat'.

23rd Jul 2019 00:08 BSTMatt Neuzil Expert

I was surprised to see a popular toilet cleaner had 9% hcl as the ingredient. Good thing I read the ingredients.

23rd Jul 2019 00:29 BSTMatt Courville

I actually found a cleaning product on e-bay (department store-style label on it) that contained what was said to be 1-3% HF in it! I read the SDS and it was really in there... I always laugh at the older generations who talk about mouthing pipettes, by which I point out that science had spit the atom by this point and still had people educated afterwards doing this??? My supervisor after years of contemplating this oddly unsafe act gave me the best explanation - rubber used for the bulbs was not available like it is today and particularly in certain countries. Imagine mouth-pipetting about serious indigestion

23rd Jul 2019 01:11 BSTA. Mathauser

Donald B Peck Wrote:


> Splashes on clothing: get out of the clothing and rinse the skin with water (the cotton clothing is going to develop holes).

And synthetic fabrics too!

When I taught in university, two of things were (and are) MANDATORY - 1) be clothed fully, 2) to remove contact lenses and wear proper goggles to shield eyes. In United States the goggles are cheap - $1 at Dollar Tree. Or hardware store (Home Depot, Lowe's, or such) - a little more money, but not much. If you would burn your eyes - or face? Better safe now than sorry later.

23rd Jul 2019 01:27 BSTSteve Hardinger Expert

Better to wear safety glasses (with proper side shields) than goggles. Goggles block peripheral vision and tend to fog. Not generally issues with safety glasses. Your safety is definitely worth the extra few dollars.

23rd Jul 2019 01:47 BSTFrank K. Mazdab Manager

One man's assessment of stupidity is another's assessment of fear-mongering. I'm reminded of the anecdote of that science fair project where the clever student hyped the threats of dihydrogen oxide, how it was the chemical responsible for more human deaths than any other and yet was wholly unregulated and even available to children! "Culture of safety" is the same excuse used by those who hide in gated communities with arsenals of weapons, because of the world outside is "scary"... a better mantra should be "knowledge is power". Now please excuse me while I go sprinkle poisonous NaCl on my dinner, admire the proven carcinogenic asbestos and uranium minerals in my mineral collection, and go swimming right after eating.

23rd Jul 2019 01:53 BSTA. Mathauser

Oh yes, of course! I always wore safety glasses - in my lab, but in university - read: a lot of ignorant students, mostly liberal majors - goggles ;-)

23rd Jul 2019 06:31 BSTKeith Compton Manager

And Frank

Don't forget your sunscreen when you go swimming in that dihydrogen monoxide stuff, and of course if down under, remember to watch for sharks, crocs and other nasties known to inhabit it! ((-:)

Oh and don't forget if you want to water down your acid, always add Acid to Water and not the other way round.

23rd Jul 2019 16:28 BSTDonald B Peck Expert

Steve, I am going to disagree with you on safety glasses (w/ side shields) vs goggles. I agree with you that goggles can "fog up" and I would add that they are a little bit uncomfortable. But they do prevent run-downs when necessary. They should be splashproof, not the type that have perforations in the body of the goggles.

A word on MSD sheets. Reading most of them can be scary. But one has to keep in mind that they are written to protect workers who handle or are in the environment with the substance 8 hours a day, about 200 days per year. That said, hazards of contact, ingestion, and in some cases inhalation still exist to infrequent handlers (like mineral collectors cleaning specimens).

Steve has it right: "Proper Safety is a Culture". Better safe than sorry.
Mineral and/or Locality is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization. Public Relations by Blytheweigh.
Copyright © and the Hudson Institute of Mineralogy 1993-2019, except where stated. Most political location boundaries are © OpenStreetMap contributors. relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: October 16, 2019 05:46:51
Go to top of page