A technique to process hypersthene in the tumbler?

I recently met a rough stone dealer here in Quebec;he has mining claims on an hypersthene occurrence(in a foliated anorthosite with a kelyphitic texture containing biotite and mafic minerals).The material is similar to the one displayed in the photo 103332 (posted for ''Wilson Lake,Labrador,Newfoundland and Labrador,Canada).It does not look like the ''bronzite'' hypersthene often seen in the market.It is opaque,so its main use if for cabbing or slabbing,but the owner of the claim told me that there is a way to tumble polish it.He was told that by one of his clients,a german lapidarist,but he does'nt know the technique used by this lapidarist.This material is unique and absolutely stunning(the photo just does'nt make justice);I really want to eventually tumble polish some.But how to do it?By using thickeners,fillers,specific grit sequences??What polishing compound should I use?Tin oxyde or something else?PLEASE help!!!

Hello!

Maybe you will just have to learn by trial and error, that usually works out in the end!

In a rotary tumbler this is my method:
I would start out with 400 - 600 grit, it may be course enough to wear them smooth. Very course grits like 80 seem to cause unwanted undercutting in some materials and small pits/chips. Best to let them roll in a generous amount of a finer grit a while longer. Re-charge the grit every 7-14 days fill barrel so the water is almost as deep as the rocks and add plenty grit the particals buffer the stones until the slurry is formed, Let them run until they become VERY smooth and free from flaws ... be patience it could take weeks or longer than a month. If you run them until all the grit is gone and only mud and stones are in the barrel that may be all you need to do as a pre-polish step. Wash the pieces carefully with soapy water. Not sure which polish to use for the final shine ... but be prepared to wait it out ... some stones take weeks or longer than a month to get a very high shine ... less water on this step but plenty of polish you want it like a drippy mud consistency ... you can pre-mix the polish and water to get the right blend.

Hope this helps ... Ray does this sound about right?

J T

John, I am no expert on tumbling of stones.. tried it and didn't like it.. Prefer to hand cab and control the outcome and it is definitely much much faster , and in my opinion, much more personally rewarding . I suspect care should be taken though, since this isn't a hard or a tough gem stone..

My friend does an excellent job with his Lake Superior agates using a combination of grinding away flaws on wheels and shaping then tumbling (see image). Hypersthene has a hardness in the 5.5-6 range that is why I recommend starting with a finer grit like 400-600.

nice agates John.
I agree that the softness demands starting fine and working slow, whether it is tumbling or cabbing,
so clearly a good call on that one, John.

Frederic and John,

In a tumbler, I find that when getting down to fine grits (500+) and polish stages, adding small plastic pellets to the mix helps cushion stones from striking each other which affects final quality of the shine. One cup pellets to each 4-5 pounds of rocks gets the job done nicely. Pellets are usually available in lapidary supply shops or hobby shops like Michaels. They stock them for stuffing dolls and pillows.

regards,

edse