picked some off a beach in north yorks this weekend, they are in shale or really soft mudstone, any ideas on how to clean them up? i’m thinking of something that will soften the shale? or shall i just get a dremel? its an excuse to buy one if nothing else….

DON’T USE ACID.

Soaking in water with Sodium hexametaphoshphate* added may soften the shale. Are they preserved in pyrite, ie goldy-looking, in which case keeping the air away long term may be important. That means a thin coat of varnish.

*And I don’t know if and where you, as a ordinary person, can buy it.

Or try a soak in water with detergent or soap.