Geodes are true geological curiosities. They are basically hollow rocks that can range in size from small nodules to large boulders. Most can easily be held in one hand. The really amazing thing about geodes is that many of them are lined with beautiful crystals of quartz, calcite or other minerals. Still others are made of agate that is banded with multi-colored layers. Polishing a geode can bring out the real beauty in the stone. While you will need some specialized lapidary equipment to polish a geode the process itself is fairly easy.
Cutting and Preparing
Imagine a line around the circumference of the geode where you wish to cut the stone in half. Draw a mark with the pencil on the geode along that line to create a guide to follow when using the wet saw to cut the stone.
Use the wet saw with a diamond blade to cut the stone. Place the geode against the saw blade following the guideline. Allow the saw to do the work and do not force the stone through the saw, as this can result in breakage of the geode. Turn the geode, cutting around the circumference of the stone until it separates into two halves.
Put a bumper pad around the outside edge of each half of the geode by wrapping each stone with rubber strips. This will prevent the geode halves from banging into each other and damaging them during the vibra-lap process.
Grinding and Polishing
Mix a grinding compound of 100 rough grit with enough water so that it will spread well and place it in the vibra-lap tray.
Turn the vibra-lap unit on. Place the geode halves face down in the grit. Allow them to work in the vibra-lap for about six to eight hours. Check occasionally to ensure the face of each geodes is being ground evenly. The face should be progressing to a completely flat surface with a dull finish that has no pits or raised bumps.
Remove the geodes halves and clean the vibra-lap, once the surface of the geode is ground flat. Mix up the next polishing compound of 220 grit. Clean the geode halves completely and start the next grinding stage.
Repeat the cleaning and grinding process using consecutively finer grits of abrasive until using a final polishing compound of 1,200 grit.