Rinse off all your rocks. In many cases, at least some of the discoloration is due to dirt, so rinsing off the rocks will help you determine how serious a rust problem you actually have.
Mix up your wood bleach solution. Wood bleach comes in a powdered form and is mixed with water to form an oxalic acid bath. Refer to the manufacturer's instructions to determine exactly how much water and powder to combine in the plastic tub.
Submerge your rocks in the solution. They will need to remain in the bath for several days. Be sure to store them out of reach of children. Wear your protective gloves when submerging them.
Rinse the rocks under running water. In the case of mineral specimens, you may wish to leave them under running water for a few hours. In the case of decorative rocks, however, you can just rinse them thoroughly for 30 to 45 minutes. Wear your protective gloves while you are rinsing, and use the scrub brush to remove any stubborn stains that are still on the rocks.
Sand off any "sticky" rust stains. If your rocks retain any stains after the oxalic acid bath, then you may need to sand them off using a fine grit sandpaper. Use light pressure and monitor the progress of the removal closely so you do not remove any more of the surface of the rock than is absolutely necessary.
Things You Will Need
- Plastic tub
- Oxalic acid (wood bleach)
- Rubber gloves
- Plastic scrub brush
- Hydrochloric acid will also clean rocks, but this acid is less common and more complicated to use than wood bleach.