Silver Blue John Marcasite Flower Ring. R815. This feminine floral Sterling Silver, Blue John and Marcasite ring features a circular central piece of Blue John that has been sourced directly from Treak Cliff Cavern in Castleton. The striking stone is surrounded by intricate petals with tiny pieces of Marcasite at their hearts. All our Blue John jewellery is designed and crafted within our very own workshops in Ashbourne, Derbyshire where a team of skilled craftsmen turn the raw Blue John stone into these stunning pieces of jewellery. You can find other matching Blue John jewellery and other Blue John rings online and instore. Silver Blue John Marcasite Flower Ring