Cleaning mould and varnish off sea shell

[Charlene]

Hi,

I purchased a beautiful Triton's trumpet about 1.5 years ago from a local in Fiji who had covered the shell in some kind of clear varnish. I've just taken a look at the shell and discovered that there are spots of black mould growing under the varnish, and the varnish is chipping off in many places.

Does anyone have any suggestions about what I should do to restore the shell? I'm worried that the mould and flaking varnish will damage the shell.

Thanks for your advice!