Whenever I used to pick up and collect stones, I would keep them in the water because they look better when they were wet as they had the “glossy” look. I always wondered how to keep them looking “glossy”? Now I know how!
How to Polish Rocks and Stones
Most stones on the beach will not polish, but there are many that will depend on the hardness of the stones. The harder stones polish best – those that look almost shiny already. Reject those stones which look grainy, they may be hard, but will not polish due to lacking the mineral qualities to polish.
One way of checking the hardness of a stone is to try to scratch it with a pen or knife. If the knife cuts a mark or produces a powdery line, then the stone will not polish. If the knife leaves a metallic line, then the stone is harder than steel and it will polish.
Tumbling times will be shorter with softer stones and a close watch will have to be kept on them, as it will not take so long to grind and polish them. Select stones that are generally 1 inch in diameter or smaller, one or two larger stones may be polished in a load that consists primarily of smaller stones.
It is a bit of a process however, it is one that gives shiny results! I think precious stones have a bit of a different method.
Open the barrel by pushing either end cap off with your thumbs. When new they are sometimes tight, but if you immerse the barrel in hot water they can be easily removed. Squeezing one side of the barrel assists when opening. If you use warm water to fill the barrel it will help to suck on the lid.
- Fill barrel ¾ full with stones and shake to settle. Do not useless, it will not work as there is no tumbling action unless the barrel is filled sufficiently.
- Add water to just over the top of the stones.
- Add 1 heaped tablespoon of coarse silicon carbide 80grit for a 1 ½ lb barrel or 2 heaped tablespoons for a 3lb barrel and 3 heaped tablespoons for a 5 lb barrel.
- Run the machine for a few days and nights while occasionally examining the stones. Fairly smooth pebbles might need only about 3 days to become nicely rounded while very jagged ones may need 10 or more days running and the grit topping up to get the same effect. 7 days is a reasonable average.
- Thoroughly clean the stones and barrel by removing both ends and draining.
- Proceed as before using 220 gritty this time. It should only be necessary to run this grade for about 5-6 days.
- Thoroughly clean stones and barrel by removing both end caps, washing carefully.
- Proceed as before using the same proportions of grit and water but this time use 400 grit. Please note this stage is very significant and determines the final polish, it is vital you do not cut it short.
- Allow at least 7 days tumbling. Do not top up with fresh grit as this will re roughen the stones. Each day on this stage imparts a smoother finish as the grit breaks down and progressively smoothes the stones making it far simpler for the next stage
- Very, very thorough cleaning the stones and barrel. It would be useful to keep one barrel to be used specifically for polishing only, because of the difficulty of cleaning grits completely from the sides of the barrel. Examine the stones very carefully and make sure that they are very smooth and discard any stones that are badly cracked or have jagged edges.
- Repeat steps as before using similar amounts of water but add one level tablespoon of cerium oxide instead of grit for a 1 ½ lb barrel (adjust amounts accordingly for the size of the barrel as with the grits). If the barrel has been cleaned out properly and the previous steps are carried out correctly 7 days running should produce gleaming stones!
Do not put any of the resulting slurries down the sink – it is inclined to set solid and we don’t want to be doing that!
I hope this helped in understanding the full process of how a stone goes from looking rough to a polished gorgeous beautiful stone that can be worn in jewelry!
I would love to visit some gem mines in Africa .. soon I hope too!