How to clean Quartz Crystals with Oxalic Acid

Cleaning quartz crystals with oxalic acid is a common practice to remove iron-oxide stains and other mineral discolorations, revealing the crystal’s clarity underneath any deposits. However, it's crucial to handle oxalic acid with care, as it can be hazardous if not used properly. Here's a step-by-step guide on how to clean quartz crystals with oxalic acid:
Pre-Step: Clean the Quartz Crystals from any remnants of clay and dirt
All crystals must be fully free from any clay or dirt. This is achieved by a regular rinsing, letting the stones dry and repeat the rinsing process. The clay will dry up in between the rinses which allows for easier removal. Clusters will most likely need to be washed with a high-pressure water stream. A pressure-washer or a spot water gun are good equipment choices for removing clay in hard to reach crevices. Using tools like dental picks or brushes is not needed or sufficient.
Any crystals with sandstone bases must be soaked for 24 hours in plain warm water before putting them into the acid. This will help with reducing discoloration and acid stains on the sandstone (The acid, especially when older can cause yellow and green stains on sandstone). You may want to choose to not clean sandstone-based specimen.
Step 1: Safety Precautions
Before you begin, ensure that you're wearing protective gear such as gloves, safety goggles, and a mask to avoid direct contact with oxalic acid fumes or skin exposure.
Step 2: Prepare the Solution
Dissolve the oxalic acid in water. Typically, a solution of one cup of oxalic acid per gallon of water is suitable for cleaning quartz crystals. Stronger solutions are ok and better than a weak solution that will lead to insufficient results.
Using a non-metallic container is preferred to avoid a chemical reaction with metal. Suitable containers include a plastic bucket, plastic tote, glass or porcelain container. I recommend using a crock pot with a strainer. This method allows one to heat up the solution for speeding up the process and removing stains more reliably.
Step 3: Soak the Quartz Crystals
Place the quartz crystals in the oxalic acid solution, ensuring they are fully submerged. Let them soak for 8-12 hours, depending on the severity of the stains, the strength of the solution and the amount of heat used. Check the crystals periodically to monitor their progress and to ensure they remain covered.
Step 4: Rinse Thoroughly
After soaking, remove the quartz crystals from the solution and rinse them thoroughly under high-pressure water. It's essential to remove all traces of oxalic acid from the crystals. Clusters will need a particular good rinsing.
Step 5 (optional):
Put the clean crystals into an ultrasonic cleaner with dish soap to remove any residues.
I do not recommend putting the crystals into a solution of baking soda (to “neutralize”) as that can cause a film on the crystals that is hard to remove. Rinsing the crystals extremely well is sufficient to remove any residual oxalic acid.
Step 6: Dispose of the Solution Safely
You can reuse the oxalic acid solution for many times. I use mine for as long as a year. If sludge builds up and results are no longer achieved, it is time to neutralize the acid. Do not pour it down the drain or dispose of it in a way that may harm the environment. Neutralizing acid is easy and cheap. All you need is either ashes (from a fire pit or fire place) or baking soda. Add as much material until the chemical reaction has ceased. I usually fill up the whole container with wood ashes. Follow local regulations for the proper disposal of the neutralized oxalic acid. Once solidified with wood ashes or through evaporation in the sun, it can be thrown away with other trash as a solid.
Final Note
Remember that oxalic acid should be handled with caution and kept away from children and pets. Always read and follow the safety instructions provided by the manufacturer. If you're uncertain about using oxalic acid, consider seeking additional advice from a seasoned miner or mining company.
Cleaning quartz crystals with oxalic acid can effectively improve the crystal’s appearance, but it's essential to prioritize safety and environmental responsibility throughout the process.
Other products such as Iron Out or Barkeeper’s Friend are also suitable options for cleaning crystals. Their active ingredient is oxalic acid as well.