You have been digging for crystals in Arkansas and after you get home, you notice there are some crystals that just don’t seem to clean up with water and brushing. They seem to have an orange stain on them. Those stains are iron, and there is only one way to get rid of them. You are going to need to purchase some oxalic acid, and I have found it in small bags sold at the mines where you dig the crystals and also on ebay.
First you will need to remove all the clay from the crystal, and I use a small dental tool or pick to remove it, and an old toothbrush to scrub it off. Then I hose off and let soak. When I’m sure it looks like there is nothing else left on the crystal, I prepare to use the oxalic acid.
If you have a small amount of crystals, you can find an old crockpot at a garage sale, and use it. You can’t use it for anything else. This will become your crystal cleaning container. Place crystals in the crock pot, add water to cover, and a few ounces of the oxalic acid. Word of caution…I wear a mask and rubber gloves, as this cannot be breathed…very dangerous to your lungs. Then I turn the crock pot on to low. Check it every day to see how it is progressing. If you need to add water, add some to keep it the crystals covered. When the crystals look clean, you are done. Turn off the crock pot and let it cool down completely. Then wearing rubber gloves, remove the crystals and rinse thoroughly. I like to do this outside with a hose, where I can use the nozzle to completely remove all residue. Set in sun and admire.
The most important thing now is to get rid of the oxalic acid. If I have more crystals to do, I can actually use the same mixture. Just add some more water and maybe an ounce or so of the acid and proceed as before. Otherwise, you may pour in an area in your yard that doesn’t have vegetation or animals and let the rain and weather wash it away. I did that when living in Arizona as I had a lot of sand and rock. However, in the city I would suggest pouring in an old container with a lid and disposing of in the trash. It is not considered hazardous.