It is not so easy to polish stones. There are specialized machines to polish them. The machines cut the stones in different angle to make them reflect light. Then it has to be taken for a chemical action.
Stone polishers look like little cement mixers. You put stones in there with polish, plug in, and come back later! You need to search for "lapidiary supplies".
To polish stone first you have to wash it with water and then put it on under the sunshine until it dries. Then you have to scrub it with a cotton towel and then put some oil on it and scrub it with a cotton towel and brush it until it shines
There are two kinds of polishing machines- tumbler and vibrator. A small tumbler (2lbs of rock) would cost about $50. It will take several weeks to polish a load. A vibrator would cost about $200 and would polish a load in a few days.