A rare shell discovered by Bermudian Jack Lightbourn in 1979 is the source of inspiration for a new Christmas decoration by Alexandra Mosher, the jewellery designer.

Ms Mosher was looking for inspiration for a new collection at the Bermuda Underwater Exploration Institute, where Mr Lightbourn’s extensive collection of shells are housed, when she came across the Pterynotus Lightbourni.

It turns out that the shell that she chose was Mr Lightbourn’s favourite out of more than 300 he discovered along with his friend, Arthur Guest. Mr Lightbourn, now 92, loved the delicate mollusc so much that he had a cast of it set in gold, which he wears around his neck to this day.

Ms Mosher’s version is a sterling silver Christmas tree decoration depicting a cross-section of the shell with pink Bermuda sand incorporated into the design. She gave one of the decorations to Mr Lightbourn as a thank-you present for giving her the inspiration.

Mr Lightbourn began collecting shells with his grandfather from the age of six, he said: “It’s nice to see people making jewellery with shell [designs] again. This is my favourite because the family it represents, Pterynotus, has a good shape: it’s very delicate and interesting to look at. To get one like this [the one he discovered in 1,000 feet of water 35 years ago] was about as perfect as you can get. It was quite a feat.”

Ms Mosher, who plans to make jewellery items inspired by the shell, added: “I loved how fine and delicate it was. It seemed to be different and unique, and it was one that Jack discovered. To me, it was the most beautiful. The fine edges were jewel-like.”

The decoration will be on sale in Ms Mosher’s store in Washington Mall, as well as at the Oceans Gift Shop at BUEI from tomorrow.