Silver Blue John Oblong Twist Ring. R001. This contemporary ring is part of our Heritage handmade jewellery collection and boasts an stunning oblong shaped cabochon of the finest Blue John stone that has been sourced locally from the Treak Cliff Cavern in Castleton. The stone is set within a simple Sterling Silver frame and completed with a classic Sterling Silver band. 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 Oblong Twist Ring. Blue John Stone 8x5mm.