I have a friend who has a selection of pearls he collected in New Guinea a little over 30 years ago. He is not sure from what oysters he got them just that he found them in oysters he collected for food. Four in particular are a spectacular pale blue colour baroque in shape and would make awesome earrings. The others are creamy and some of them are quite round. What I would like to know is how to clean them up. He has a tumbler (he is a jeweller) but doesn't know what material (I read somewhere maybe it is pumice?) to tumble them in. Could someone please advise me as to technique for tumbling pearls.
Thank you in anticipation,