Whitby Jet Locket Round Marcasite Silver. P2148. This enchanting necklace boasts an unmissable diamond shaped piece of fine Whitby Jet stone that has been sourced directly from the north east coast of Yorkshire. The stone is set within the centre of a mesmerising sterling silver locket that has been embellished with dazzling marcasite stones, giving the piece a sophisticated sparkle. The locket hangs from a delicate sterling silver chain complete with a classic bolt ring clasp for easy wear. 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 necklaces on our website. Sterling Silver and Whitby Jet.