Hi and welcome amongst us Pearl Guiders,
Could you post a photo?
I hope the strand consists not of shell pearls, that would be fake pearls made out of mother of pearl. They always look perfect (no blemishes and fine luster). But as you say there are grooves, that canīt be, the size of 30 mm does sound gigantic for "real" pearls, whatever mollusk they might have come from...
Anyway, if you like the strand you should wear it with pride regardless wheter itīs real or not. If they are Shell pearls, I think you paid a high price.