Silver Blue John Marcasite Large Heart Locket Necklace. P2149. This romantic, vintage style pendant boasts a highly polished heart shaped piece of the finest Blue John stone that has been sourced directly from the Treak Cliff Cavern, Castleton in Derbyshire. The stone is set within the centre of a sterling silver heart locket that has been embellished with a dazzling marcasite stones, giving the piece a sophisticated sparkle. The locket hangs from an 18 inch long sterling silver chain complete with a classic bolt ring clasp for easy wear. All our Blue John jewellery is designed and crafted within our very own workshops in Derbyshire where a team of skilled craftsmen turn the raw Blue John into these stunning pieces of jewellery. You can find other matching Blue John jewellery and other Blue John necklaces on our website. Silver Blue John Marcasite Large Heart Locket Necklace. Drop including bail 39mm, locket 26x26mm.