Cleaning a crystal (Iron stains??)

Many people use oxalic acid solution to remove iron stains from quartz. There is also hydrochloric acid, citric acid or CLR solutions that all remove iron as well.

Pool and spa acid is super strong... Gets the job done.

Outdoors, with gloves and eye protection, crappy old clothes....

I play around with various chemicals to see how effective they are on various rocks. So I am not a professional and am not offering advise. I will just state the following for education purposes.

At times, it depends on how patient you are, cost, fumes and disposal. With almost any of them, working outside and staying upwind is prudent. If you dilute, add the water first and not the acid. Harsh chemicals usually come with a warning to wear appropriate gloves and eye protection. Read the labels. Don't use a metal container.

With some mild acids like vinegar, they can sometimes be more effective if you add heat and/or salt. I only add salt to clean metals (eg coins or silver ore). Never heat a strong acid.

IMHO - CLR is expensive and only somewhat effective, but you can use it indoors. However, as with most chemicals/acids, immediately clean up any drips on your kitchen counter tops, as they can remove the colour. If I have time, I use vinegar for mild etching or cleaning. It may take overnight, a week or more. Real Coke is actually a mild acid too, but a bit expensive for cleaning rocks. For iron stains, standard Iron Out is pretty good. At my local stores, it is a powder in the same size and shape bottle as CLR and costs about the same - -as such, it is way more price effective than CLR for cleaning iron stains. Next up is muriatic acid from a pool/spa supply store (less cost than the big box stores sell it). I can get 4L for about the same cost as a bottle of CLR. Muriatic acid needs to be treated with care. It is fast, sometimes too fast, and it can bubble high in your container (read overflow). I start with 50:50 water:acid or less. you can always add more later. For disposal, I use it like Roundup on plants (even after it has turned to base with calcite); it will kill anything that gets sprayed. Don't mix one chemical with another - do them one at a time.

Thanks for the advice.

I got some CLR a few days ago and put the rocks in. They are very slowly getting cleaner, though the difference isn't huge. I still see bubbling from the bit of calcite lodged in the crystal so it must not be finished cleaning the rocks.

I have some super iron out coming to me in the mail so I'll try that next outside.

I have battery acid, which is sulfuric acid if I remember right and can try that out if you think it might work. I have muriatic acid (HCl) back in Connecticut (16 hour drive away at the moment) so I can't try that just yet. Unfortunately I doubt my local area sells any of that at all. They didn't even have super iron out.

Is there any way to repair or fill in the cracks in the crystal?

Well I had the rocks in some CLR for about a week. It dissolved out the calcite that was stuck onto the quartz in a few places and cleaned the crystals up little. But the rust colored brown stains are still stuck in the cracks. I bathed the rocks in distilled water for a few hours to remove the CLR and then sealed them into a pickle jar with super iron out & some distilled water.

Not sure what all the reviews on amazon are talking about "fumes & vapors," I didn't smell any and no gas was released from the pickle jar either. Just to be safe I put it outside. I'll check on it tomorrow, hopefully nobody steals the rocks.

I wonder how long it will take to get rid of the stains (if they are iron stains at all?).

I have battery acid (sulfuric acid) I can try that out next. A bit stronger than citric acid

No surprise that acid is working with calcite and marble (meta-limestone / lime-muds). Acid + carbonate -> CO2 & Oxides. I'm just surprised that its not eating away the desired minerals and just leaving you with only the dirt!

These came from that batch. They were coated with red clay.

The super iron out is working well. I have it in a pickle jar with the lid on in the back of my car. It heats up during the day and as I drive around to work and back the liquid is jostled back and forth which has helped clean out most of the iron in the cracks. There is still a bit left to go but I'm hoping it should be completely cleared out by the end of the week.

Will post some photos when I'm done.

Does anyone know if it is possible to seal the cracks in some way? I know that they do this with gemstones somehow (lead glass?). Is this an easy process that you guys have used in the past or is it essentially impossible at the hobbyist level?

I'll check the lid again tomorrow for corrosion but it has a plastic coating over the lid to protect it from the salty pickle juice so that might be buying me some time. I've also got it in a plastic tub incase of spills. The solution was water clear as of about 4 pm today, but I'll keep an eye out for yellowing. I certainly wouldn't want to redeposit the iron. That would be most unfortunate especially since it is starting to look so good.

Is there any technique I can use to fill in cracks in quartz crystals that you guys know of?