Should I insure this necklace?

18 years ago I opened an oyster on a holiday and got a pearl from it. I have the certificate etc. this year my parents had it made into a necklace for me. In 1996 the pearl was worth less than £50 but I'm not sure if value goes up over time? Should I be getting this necklace insured?

It was a cultured pearl from Japan.

Thank you!