Cleaning Agates with Muriatic Acid (5 Tips To Read Before You Start)

Muriatic acid (like many products) is frequently referenced in articles about cleaning up rocks.

It can work really well, but isn’t a good general use solution. In this article, we’ll teach you what you need to know about cleaning agates with muriatic acid.

Muriatic Should Only Be Used If You Are Cleaning Off Something The Acid Works On

It is pretty easy to just dump your rocks into a solution and hope that the rock looks amazing when you pull it out.

Sadly, this doesn’t work in every case with muriatic acid. In fact, unless your specimen has something on it’s surface where the acid can reach that will react with the acid, it is unlikely that the acid will do anything at all.

If you have a piece that is covered in calcite, or has a lot of iron oxide rust staining, then muriatic is a good solution for you.

But if what you want is to remove outer layers of other minerals that are obscuring the underlying minerals you want to expose, the sad truth is that it might not do anything at all.

Will Muriatic Acid Damage An Agate?

It helps to understand what agates actually are.

Agates are actually a form of quartz, and they are pretty hard like other forms of quartz, similar to amethyst and carnelian. They are a 7 out of 10 on the Moh’s Hardness Scale.

You can find them around the world, including near Yellowstone National Park.

Agates are composed of silicon dioxide. Silicon dioxide is a material that actually acts a bit like an acid itself, and if it does react, it tends to do so more often with bases.

Because silicon dioxide is unlikely to react with acids like muriatic acid (aka hydochloric acid), then putting a piece of agate that is purely agate material is unlikely to do anything at all.

That being said, an agate is often something that we pick up and think of it as a whole, rather than its constituent parts. The agate that you pick up on the beach is beautiful not only because of the agate, but also because of the other materials attached to it, curving around it, or even through it.

If you look at the agate as a whole piece, it is possible that muriatic will do damage to materials on the stone that you did not want to be changed.

Foe example, if your agate is set in a piece of calcite, and the rock looking really beautiful because of that calcite, putting the piece in muriatic will damage it because it will dissolve the calcite.

Tips for Cleaning Agates With Muriatic Acid

We have a general tutorial article that covers the basics of actually using muriatic acid to clean rocks: Cleaning Rocks With Muriatic Acid: 3 Things You Should Know

But before you move forward with muriatic acid, here are our recommendations:

  • Make sure that you are sure you understand what types of material your stone is made up of. If you don’t have anything that muriatic acid works on, then there is no point in purchasing, using, and cleaning up such a volatile substance. Instead, consider working with other cleaners or products that will actually help.
  • Have a plan for what you want the acid to achieve, and make sure you think through whether muriatic acid will help you get to that point. Some people collect rocks and then just decide to throw them into a solution to make them prettier, cleaner, or shinier. This is a recipe for frustration. Sometimes people want to take a piece down dramatically in size, or they want to expose something deep on the inside. In some cases, it is better to cut the piece or even grind it down. You’ll have a lot more control that way. Putting a piece in acid is sort of like letting the horses out and watching where they run.
  • Set up a neutralizing station before you set up your acid station. This means that you should fill up a bucket of water and put a bunch of baking soda in it before you do anything with the acid. This way you’ll be prepared to clean up any spills, or to stop the reaction right away by dropping the stone into the neutralizing bath if the acid is working too quickly or looks like it is reacting in a dangerous way (think dark fumes).
  • If you aren’t sure how well the muriatic acid will work, but you have a piece that you really value and fear damaging, the best thing to do is to try out the acid bath with a test piece. Try and find another piece that is similar in composition, though it doesn’t have to be the same size. Sometimes what you will find is that the acid actually eats up some of the materials that make the piece extra colorful or beautiful. And you only realize it after the fact.
  • Don’t accept what people say on the internet or YouTube about whether muriatic acid will work on a piece. In many cases, these creators haven’t actually even tried the method that they are recommending. So much of rockhounding is about experience, learning by doing. Articles and videos are great, and can help you build a foundation, but nothing replaces trying it yourself. If you are still in the information consumption mode, look for videos that actually show the acid in frame, show the rocks before, going into the solution, and then after. I think this video is a good example of someone who is trying hard to make useful content (even if he isn’t an expert).

Alternatives to Muriatic Acid When Cleaning Agates

In general, before I even think about dropping my agates in muriatic acid (which I rarely do because it is so dangerous to have around and use), I start with cheap and easy methods.

  • First, I soak my agates in regular water.
  • Then I scrub my rocks with a brush, a toothbrush if they are small.
  • I’ll use a pick to see if anything can be gently picked out or scraped out.
  • I’ll scrub the stones with dawn dishsoap.
  • Then I’ll rinse and allow the stones to completely dry so I can see what I’m working with.

Once I have a baseline for where the stones are at, I will make my next step decisions. For rocks that I want to brighten up a bit (and I don’t have concerns about dissolving calcite), I’ll soak them in vinegar. For rocks that are covered and stained with organic plant matter, I might consider a weak bleach solution.

And if the rocks just look rough, I might consider tumbling them to see if the edges can be smoothed out.

There isn’t any one way to clean agates. Start with the least intrusive method and then work your way through until the stone looks the way you want it to.

Want to learn more about caring for the rocks you’ve collected? Check out our Knowledge Vault for articles to learn more rockhounding tips and tricks.