To clean an amethyst cathedral, or geode, inspect the interior for minute minerals, brush away external dirt, soak the crystal in either a salt or bleach bath and polish the crystal with denture cleaner. Cleaning an amethyst cathedral takes roughly one hour plus soaking time and requires a bristle brush, salt or bleach, an electric toothbrush and denture cleaner.
- Check for tiny minerals
Before soaking the amethyst cathedral, inspect the interior for sand-sized minerals, such as geothite, millerite or kaolinite. If they are loose, shake them out. However, if they are fused to the inside of the geode, they may become damaged by cleaning. The presence of an iron oxide stain likely means these minerals are not present.
- Brush off visible dirt
Use a bristle brush or toothbrush to remove any visible dirt from the exterior.
- Soak in salt water
Fill a glass bowl with water and sea salt. Place the crystal inside, and allow it to soak for up to 24 hours. Rinse it with cool water.
- Soak in bleach water
If the amethyst cathedral is very gritty, omit the salt water soak. Instead, place it in a tub of warm water with a quarter-cup of bleach. Let it soak for 24 to 48 hours. Rinse it with cool water.
- Polish with an electric toothbrush
Apply denture cleaner to an electric toothbrush. Use this to polish the interior of the geode until all the remaining grit is gone and the crystal is shiny.