Silver Whitby Jet Marcasite Dragonfly Brooch. M328. This gorgeous dragonfly brooch is hand made in Sterling Silver and features a beautifully hand carved Whitby Jet gemstone set in the body and sparkling Marcasite gemstones set in the wings and tail. This is an exquisite and detailed piece which would make a beautiful gift. The Whitby Jet stone has been directly sourced from the north east coast of Yorkhire. All our Whitby Jet jewellery is designed and crafted within our very own workshops in Derbyshire where a team of skilled craftsmen turn the raw Jet into these stunning pieces of jewellery. You can find other matching Whitby Jet jewellery and other Whitby Jet brooches on our website. Silver Whitby Jet Marcasite Dragonfly Brooch. 29mm x 29mm, Whitby Jet 7x5mm.