Bruise I believe sand would be a fine idea. There's usually more than one grade of sand in a sand deposit in the bush.
And since an abrasive works best with a little lubricant, like soap, you may have that in your supplies.

If not in many parts of the country there are certain plants that yeild a soap like substance that will keep you and your hair clean.
No one says it can't be used for cleaning hones as well.
AFAIC there's no such thing as disposable Ceramic anything.
A little more info on the sand you might find interesting is that the American ndns used sand for a myriad of finishing techniques both on very hard wood and stone.
The Indin Pipes we talked about some while back were once finished with natural sand as that's all there was to finish stone with.
The sand was carefully seperated and was often traded long distances.
This is from oral traditions so it may not be accurate

according to the non-ndns.

The very beautiful hard rock maple round ball warclubs from the Northeast were often finished using fine grades of sand.