There are as many cleaning methods out there as there are rockhounds. There’s no one correct way to clean every specimen, so it helps to experiment with different things.
This time around I’m going to show you how to clean rocks with hydrogen peroxide, and discuss how you can decide if it’s the right way to go for specimens you’ve gathered.
Without further ado, let’s dig in and get to cleaning!
What Hydrogen Peroxide Does to Rocks
Hydrogen peroxide is a nasty, nasty chemical. At least when we’re talking H₂O₂ in 30% or higher concentrations. Most of us are used to the household stuff, sitting at a solid 2-3%, or even hair bleach which is around 10%. These are fairly benign.
Don’t muck around with high concentration hydrogen peroxide even if you know where to find it. It’s unnecessary for cleaning stones and it’s not in your best interest to even have it around.
We’ve got two cleaning actions that show up with the mixture we’re going to use.
- Mechanical- Hydrogen peroxide bubbles can dislodge dust, clay, and other remnants left behind from digging the stone out. It works better than just soap and water in many cases, especially when you’ve got a lot of small cracks and crevices to deal with.
- Chemical- Hydrogen peroxide will dissolve most organic stains readily. These are relatively rare on mineral samples, but with a little bit of added acid you’ll find that H₂2O₂ will also dissolve manganese oxides and a few other staining impurities.
When it comes to getting specimens clean, every little bit helps.
The bubbling action from the chemical isn’t actually a chemical reaction with the surface it’s in contact with. Instead, it’s just a catalytic reaction as the hydrogen peroxide breaks down into oxygen and water.
Hydrogen peroxide is a good way to go for stones that have manganese staining and those which have deep crevices.
Manganese staining is relatively common, especially in stones that have been sourced in deserts. It forms as an orange-to-black patina on the surface of the stone and it’s a common blemish on some specimens. The darker variants are sometimes called desert varnish.
Hydrogen peroxide sometimes works on iron stains as well, at least if they’re not too deep. In many cases, harsher chemicals may be needed to fully clean them off of stones like quartz or amethyst.
That said, a lot of stones will benefit. Rough agates, in particular, often have pockets that can be hard to clean out with the usual methods and can be dislodged by the bubbles formed.
What You Need
This is a simple process and doesn’t require much. You’ll want to gather the following:
- Hydrogen Peroxide (2-3% concentration)
- White Vinegar
- Sponge or Brush
- Dish Soap
- A Suitable Container
- Old Tooth Brush
- Wire Brush
These are all pretty common household items. However, if you don’t have them on hand, you can easily get them from Amazon by using the list below.
Any Safety Concerns?
For this cleaning method, we really don’t need PPE for anything that’s going on but goggles aren’t a bad idea if you’re very wary of chemicals.
You may also want some gloves, the vinegar smell will stay on your hands for some time otherwise.
Step 1: Pre-Clean With Soap and Water
First things first: you want to get the stones as clean as possible without resorting to chemical methods.
Use your usual method for cleaning. I run the sink into a bowl and then add Dawn dish soap. A sponge or brush, depending on the sample, then does most of the work.
This method works great for just getting the surface but it’s not perfect. It doesn’t do anything chemically, and it can be hard to dislodge clay and dirt from inside fractures and other surface features that lead deeper into the stone.
A good wash is always the first thing to do. You can only decide which route to take once you’ve handled the basics.
Step 2: Prepare Container and Solution
You’ll now want to put on your mad scientist goggles and begin creating your secret rock cleaning solution. It’s a proprietary secret in many places.
You’ll just want to mix 1:1 ratios of household white vinegar and hydrogen peroxide. Just pour both into your jar, bowl, or any other suitable container, and then mix them together.
You may see some bubbles, but this won’t generate any heat or cause any reactions. Instead, it leaves you with a slightly acidic hydrogen peroxide solution that’s ready to do the heavy lifting on some stains for you.
Step 3: Soak Your Rocks
Get your rocks in quickly, hydrogen peroxide only lasts so long.
If you have an unknown sample that begins massively bubbling after dropping it in then I recommend pulling it, drying it off, and setting it aside for further testing. Normal fizzing bubbles are fine, and most rocks will generate at least a few.
In my case, the crystal formation (likely quartz) and the matrix were pretty much inert. Some surface bubbling began to push bits of plant matter I hadn’t been able to get to out of several crevices in the stone.
Due to the collection region of the stone, I believe the slight orange staining is most likely oxidized iron and won’t be removed during the process.
Leave the rocks alone for 15-30 minutes, depending on how much time you have.
Step 4: Wire Brush and Dry
Remove your stones from the solution and take a good look. If you identified manganese stains before and they’re not gone, then you may want to just quickly brush at them with your wire brush to see if they’ll come off yet.
If not, put them back into the solution. The hydrogen peroxide will keep working until it’s no longer fizzing at all, which means it’s broken down entirely into water.
The wire brush should remove any build-up that’s been loosened. Try really getting in there on cracks and other features. Use steel if possible, but if you have a softer stone then brass is probably a better option. For really soft stones you can use a nylon brush, but they don’t remove contaminants as well.
An old toothbrush is good for deeper cavities, where metal or steel wire brushes will just bend on you.
In my case, the stone was cleared of some surface impurities that were brown in color. More importantly, the hydrogen peroxide pushed the dirt and plant matter out of the crevice pictured above!
That I wouldn’t have been able to accomplish only by hand.
After you’re done there, all you need to do is dry the stone off and decide what you’re going to do with it next. It may need further cleaning, or it could be ready for whatever you’re planning on next.
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